Easy Homemade Onion Soup Recipe UK – Delicious Soup Using Homegrown Onions

There’s nothing quite like a delicious bowl of homemade onion soup, especially on a cold autumn or winter evening after spending the day working on the allotment.

If you’ve harvested plenty of onions from your garden, this homemade onion soup recipe UK is a fantastic way to use them.

With slowly caramelised onions, garlic, rich vegetable stock and a few simple herbs, you can create a wonderfully comforting soup without spending a fortune.

The best part is that you don’t need expensive ingredients or complicated cooking equipment.

You can make this soup in an ordinary saucepan, and I’ll also explain how to adapt the recipe for a soup maker.

Here at Gardening with Ben, I love finding practical ways to use the vegetables we grow on the allotment.

After all, there’s no point growing a fantastic harvest if you don’t get to enjoy eating it!

Whether you’re using homegrown yellow onions, red onions or onions bought from your local supermarket, this simple recipe makes a warming and satisfying meal.

Why You’ll Love This Homemade Onion Soup Recipe

There are plenty of reasons to give this recipe a try.

• Budget-friendly: Onions are inexpensive, particularly when you’ve grown your own.
• Simple ingredients: Most of the ingredients are everyday kitchen essentials.
• Full of flavour: Slowly cooked onions develop a delicious natural sweetness.
• Vegetarian-friendly: Use vegetable stock and suitable vegetarian cheese.
• Perfect for batch cooking: Make extra portions for another day.
• Freezer-friendly: Freeze the soup without its bread or cheese topping.
• Great for winter: Ideal after a chilly morning gardening.

The secret to really delicious onion soup is taking your time when cooking the onions.

Homemade Onion Soup Recipe at a Glance

Details	Information
Recipe	Homemade onion soup
Cuisine	British-style onion soup inspired by French onion soup
Preparation time	15 minutes
Cooking time	55–65 minutes
Total time	Approximately 70–80 minutes
Servings	4
Difficulty	Easy
Suitable for	Vegetarian diets when using suitable stock and cheese
Freezer-friendly	Yes, without toppings

Ingredients for Homemade Onion Soup

This recipe makes approximately four servings.

Main Ingredients

• 750g onions, peeled and thinly sliced.
• 30g butter.
• 1 tablespoon olive oil.
• 2 cloves garlic, finely chopped.
• 1 litre vegetable stock.
• 1 tablespoon plain flour, optional for thickening.
• 1 teaspoon fresh thyme leaves or ½ teaspoon dried thyme.
• 1 bay leaf.
• 1 teaspoon Worcestershire sauce, optional (choose a vegetarian version if required).
• Salt and freshly ground black pepper, to taste.

Optional Cheesy Toast Topping

• 4 slices of crusty baguette or other suitable bread.
• 75g grated mature Cheddar or Gruyère cheese.
• A little butter or olive oil for the bread, if desired.

If you’re cooking for vegetarians, check the cheese uses vegetarian rennet, and make sure your Worcestershire sauce is suitable.

You can also leave the cheese topping out entirely for a lighter soup.

Which Onions Are Best for Homemade Onion Soup?

One of the wonderful things about onion soup is that you can use several different onion varieties.

Yellow Onions

Ordinary yellow or brown-skinned onions are my first choice.

They offer a good balance of natural sweetness and savoury flavour.

When cooked slowly, they develop a lovely deep golden colour.

If you’ve grown varieties such as Sturon or Centurion on your allotment, they’re excellent options.

Red Onions

Red onions can also be used.

They often produce a sweeter flavour when cooked, although the finished soup may have a slightly different colour.

You can also mix red and yellow onions.

White Onions

White onions work well and create a delicious soup.

Their flavour can differ slightly from traditional yellow onions, but they’re still a useful option.

Homegrown Onions

Of course, there’s something extra special about using onions you’ve grown yourself.

Whether you’ve harvested autumn onion sets or spring-planted onions, using your own produce makes the meal particularly rewarding.

Just make sure the bulbs are firm, healthy and free from any signs of rot.

How to Make Homemade Onion Soup: Step-by-Step

Let’s get cooking!

Step 1: Prepare Your Onions

Peel the onions and remove the outer skins.

Cut each onion in half, then slice thinly.

Try to make the slices a similar thickness so they cook evenly.

Don’t worry if your eyes start watering — that’s part of the onion-chopping experience!

Step 2: Heat the Butter and Oil

Place a large, heavy-bottomed saucepan over a medium-low heat.

Add the butter and olive oil.

Allow the butter to melt gently.

Using both butter and oil gives the soup a lovely rich flavour.

Step 3: Add the Sliced Onions

Place the sliced onions into the saucepan.

Stir thoroughly so they’re coated in the butter and oil.

Add a small pinch of salt.

Cook gently for approximately 10 minutes, stirring occasionally, until they begin softening.

Step 4: Slowly Caramelise the Onions

Reduce the heat if necessary.

Continue cooking the onions for approximately 25–35 minutes, stirring regularly.

You want the onions to turn a deep golden-brown colour.

This stage is important.

Slow cooking allows the onions to develop their sweetness and rich flavour.

Don’t rush the process by turning the heat up too high.

If the onions start sticking or burning, add a small splash of water and lower the heat.

Gardening with Ben tip: The longer you gently caramelise the onions without burning them, the richer and more satisfying your soup will taste.

Step 5: Add the Garlic

Once the onions are caramelised, stir in the chopped garlic.

Cook for another minute or two.

Avoid allowing the garlic to burn because it can become bitter.

Step 6: Add the Flour

If you prefer a slightly thicker soup, sprinkle in the tablespoon of plain flour.

Stir well and cook for approximately one minute.

The flour is optional.

You can leave it out if you prefer a lighter, thinner broth.

Step 7: Add the Stock and Herbs

Gradually pour in the vegetable stock while stirring.

Add the thyme and bay leaf.

If you’re using Worcestershire sauce, add it now.

Bring everything to a gentle simmer.

Step 8: Simmer the Soup

Allow the soup to simmer gently for approximately 15–20 minutes.

Stir occasionally.

This gives the flavours time to combine.

Taste before adding additional salt, as some vegetable stocks are already quite salty.

Add freshly ground black pepper to taste.

Remove the bay leaf before serving.

Step 9: Prepare the Cheesy Toast

While the soup simmers, lightly toast the bread.

Sprinkle the grated cheese over the slices.

Place under a hot grill until the cheese has melted and begun turning golden.

Keep an eye on it so the bread doesn’t burn.

Step 10: Serve and Enjoy

Ladle the hot onion soup into bowls.

Place a slice of cheesy toast on top or serve it alongside.

Finish with a little freshly ground black pepper or fresh thyme.

Your homemade onion soup is ready to enjoy!

How to Make Onion Soup in a Soup Maker

If you’ve got a soup maker, you can also prepare a delicious onion soup using your homegrown onions.

However, traditional onion soup gets much of its flavour from slowly caramelising the onions.

Most soup makers don’t provide the same caramelisation as a saucepan.

For the best results, I recommend cooking the onions in a frying pan before transferring them.

Soup Maker Ingredients

For a typical soup maker, use:

• 400g sliced onions.
• 15g butter.
• 1 teaspoon olive oil.
• 1 small garlic clove.
• Approximately 450–600ml vegetable stock, adjusted to your machine’s capacity and fill markings.
• ½ teaspoon dried thyme.
• Freshly ground black pepper.

These quantities suit many medium-sized soup makers, but always follow your manufacturer’s minimum and maximum fill levels.

Soup Maker Method

1. Melt the butter and oil in a frying pan.
2. Add the sliced onions.
3. Cook gently for approximately 25–35 minutes until golden and caramelised.
4. Add the garlic and cook for another minute.
5. Transfer the cooked onions into your soup maker.
6. Add the thyme, pepper and enough stock to reach the permitted fill level.
7. Select the appropriate programme for a hot soup.
8. Once complete, taste and adjust the seasoning.
9. Serve with toasted bread or cheese-topped croutons.

Should You Use the Smooth or Chunky Setting?

That depends on your preference.

Chunky setting: Best for a more traditional onion soup with visible onion pieces.

Smooth setting: Creates a blended soup with a creamy texture, even without cream.

If your machine only provides a smooth programme, that’s perfectly fine.

Just remember that the texture will be different from traditional French-style onion soup.

Never exceed the manufacturer’s maximum capacity or add ingredients that your particular machine doesn’t support.

What Is the Secret to Really Good Onion Soup?

The secret is caramelisation.

Onions contain natural sugars that develop rich, complex flavours as they cook slowly.

When onions are properly caramelised, they become soft, sweet and golden brown.

If you rush this stage, the soup may taste more like ordinary boiled onions.

For the best results:

• Slice the onions evenly.
• Cook them slowly.
• Stir regularly to prevent burning.
• Use a heavy-bottomed pan.
• Avoid adding the stock too early.
• Use a good-quality stock.

Patience makes a tremendous difference.

Can You Make Onion Soup Without Butter?

Yes.

For a dairy-free or vegan version, replace the butter with olive oil or another suitable cooking oil.

Use vegetable stock.

Leave out the cheese topping or use a suitable plant-based alternative.

The onions will still develop plenty of flavour when caramelised properly.

How to Make Vegetarian Onion Soup

This recipe is easy to adapt for vegetarians.

Use vegetable stock rather than beef stock.

Choose cheese made with vegetarian rennet.

If adding Worcestershire sauce, select a vegetarian variety because traditional Worcestershire sauce often contains anchovies.

You can also use a small splash of soy sauce for extra savoury flavour, although this changes the recipe slightly.

For a completely vegan onion soup, use plant-based butter or olive oil and omit dairy cheese.

Can You Make Onion Soup Without Wine?

Absolutely.

Many traditional French onion soup recipes contain white wine, but it’s not essential.

This recipe doesn’t require wine at all.

Slowly caramelised onions, garlic, thyme and good stock provide plenty of flavour.

If you’d like a little extra acidity, add a small splash of cider vinegar towards the end of cooking.

Taste carefully before adding more.

How to Make Onion Soup Thicker

If you prefer a thicker soup, there are several options.

Add a Little Flour

Adding a tablespoon of plain flour after caramelising the onions can thicken the broth slightly.

Blend Some of the Soup

Remove a small portion, blend it until smooth and return it to the saucepan.

This creates a fuller texture without adding cream.

Simmer for Longer

Allowing some liquid to evaporate will concentrate the soup.

However, remember that the flavour and saltiness can also become stronger.

Add a Small Potato

For a less traditional but heartier soup, add a small peeled and diced potato during simmering, then blend once it’s completely cooked.

This works particularly well for smooth soup-maker recipes.

What Can You Serve With Homemade Onion Soup?

Homemade onion soup can be served as a starter or as a warming lunch.

Some delicious accompaniments include:

• Crusty bread.
• Cheese-topped baguette slices.
• Homemade garlic bread.
• Toasted sourdough.
• A simple green salad.
• Homemade cheese scones.
• A warm bread roll.

If you’re using homegrown onions, you might also like to add fresh herbs harvested from your garden.

Thyme works particularly well.

Can You Freeze Homemade Onion Soup?

Yes!

Homemade onion soup freezes well, making it useful for batch cooking.

For the best results, freeze the soup without the bread and cheese topping.

How to Freeze Onion Soup

1. Cook the soup and remove the bay leaf.
2. Cool it quickly, dividing large quantities into smaller containers if necessary.
3. Place into suitable freezer-safe containers.
4. Leave appropriate expansion space according to the container instructions.
5. Label with the date and contents.
6. Freeze promptly.

For best flavour and quality, aim to use frozen onion soup within approximately three months.

Keep your freezer at around -18°C.

Thaw in the fridge, then reheat until steaming hot throughout.

Avoid reheating the same leftovers repeatedly.

How Long Does Homemade Onion Soup Last in the Fridge?

According to UK Food Standards Agency guidance, cooked leftovers should be cooled and refrigerated within one to two hours.

Use refrigerated leftovers within 48 hours or freeze them.

Store onion soup in a covered container in the fridge.

When reheating, make sure it’s steaming hot throughout and reheat only once.

These simple precautions help keep homemade meals safe.

Can You Use Frozen Onions to Make Onion Soup?

Yes.

If you’ve already frozen some of your onion harvest, you can use those onions to make soup.

Frozen onions tend to release more moisture during cooking.

This means they may take longer to caramelise.

Add them to a suitable pan and allow the excess water to evaporate before cooking them until golden.

Fresh onions are generally easier to caramelise, but frozen onions can still produce a delicious soup.

How to Make a Budget-Friendly Onion Soup

One of the best things about homemade onion soup is that it doesn’t require expensive ingredients.

If you’ve grown the onions yourself, the main ingredient is already available.

For an inexpensive version, use:

• Homegrown or budget yellow onions.
• Vegetable stock cubes.
• A little cooking oil.
• Dried thyme.
• Black pepper.
• Leftover bread for serving.

You can leave out the cheese topping to reduce the cost further.

It’s a great example of how growing your own vegetables can help you prepare satisfying meals using simple ingredients.

Common Mistakes When Making Onion Soup

1. Not Cooking the Onions Long Enough

This is probably the biggest mistake.

Proper caramelisation gives onion soup its distinctive richness.

2. Cooking the Onions Too Quickly

High heat can burn the onions before they’ve softened and developed sweetness.

3. Adding Too Much Salt

Stock can already contain plenty of salt.

Taste the finished soup before adding more.

4. Using Too Much Liquid

Too much stock can produce a watery soup with weak flavour.

5. Burning the Garlic

Garlic cooks faster than onions.

Add it near the end of caramelisation.

6. Forgetting to Remove the Bay Leaf

Remove whole bay leaves before serving or blending the soup.

7. Using Rotten Onions

Only use healthy onions.

Discard bulbs showing mould, serious decay or unpleasant smells.

8. Freezing the Soup With Bread Toppings

Bread and cheese toppings generally taste better when prepared fresh.

Freeze the soup separately.

Frequently Asked Questions About Homemade Onion Soup

What is the best onion for homemade onion soup?

Yellow or brown-skinned onions are excellent because they develop a rich, sweet flavour when slowly caramelised.

Can you make onion soup with red onions?

Yes. Red onions can produce a delicious soup, although the colour and flavour may differ from traditional versions.

Can you make onion soup in a soup maker?

Yes. For the richest flavour, caramelise the onions in a frying pan before transferring them into your soup maker.

Do you need to add flour to onion soup?

No. Flour is optional and is mainly used to create a slightly thicker consistency.

Can you make onion soup without cream?

Absolutely. Traditional onion soup doesn’t require cream.

How long does onion soup take to make?

Allow approximately 70–80 minutes for preparation and cooking, including time to caramelise the onions properly.

Is homemade onion soup vegetarian?

It can be. Use vegetable stock and ensure any cheese and Worcestershire sauce are vegetarian-friendly.

Can you freeze homemade onion soup?

Yes. Freeze the soup without toppings, ideally using it within approximately three months for best quality.

Why does my onion soup taste bitter?

Burnt onions or garlic can create bitterness. Cook slowly and avoid scorching the ingredients.

Can you use frozen onions for onion soup?

Yes, although you may need additional time to evaporate their moisture before caramelising.

What herbs go well with onion soup?

Thyme and bay leaves are excellent choices. A little rosemary or parsley can also be used.

Can I make onion soup the day before?

Yes. Cool and refrigerate it promptly, then reheat thoroughly before serving. Follow UK food safety guidance for leftovers.

Final Thoughts: Enjoying Homemade Onion Soup From Your Allotment

Making a delicious homemade onion soup recipe UK is a wonderful way to enjoy the onions you’ve grown in your own garden or allotment.

It’s a simple, warming meal that makes the most of everyday ingredients.

Whether you prefer traditional onion soup with caramelised onions and cheesy toast or a smooth version made in a soup maker, there’s something particularly satisfying about cooking with your own harvest.

My biggest piece of advice is to take your time when caramelising the onions.

That one step transforms a few simple vegetables into a rich and comforting soup.

And if you’ve had a particularly successful onion harvest, why not make a larger batch and freeze some portions for those cold winter evenings?

I hope you enjoy giving this recipe a try.

Thanks for joining me here at Gardening with Ben, and happy cooking!

Keep smiling, keep shining, keep gardening with Ben!