Delia Smith French Onion Soup Recipe

This is my cosy, deeply savoury take on Delia Smith’s classic French onion soup, with properly caramelised onions, a rich beefy broth, and that golden, bubbling cheese toast on top. The texture is silky and comforting, with sweet onions balanced by a gently savoury, wine-kissed stock. It’s a medium-difficulty recipe mainly because good caramelisation takes patience, but the steps themselves are simple. Allow about 1 hour 15 minutes from start to serving.

Ingredients

For the onion soup

• 1kg onions, thinly sliced
• 50g unsalted butter
• 1 tbsp olive oil
• 1 tsp fine salt (plus more to taste)
• 1 tsp caster sugar (optional, helps browning)
• 2 garlic cloves, finely chopped
• 1 tbsp plain flour
• 150ml dry white wine (optional)
• 1.2 litres hot beef stock
• 2 tsp fresh thyme leaves (or 1 tsp dried thyme)
• 1 bay leaf
• Freshly ground black pepper, to taste

For the cheesy toasts

• 6 slices baguette (about 1.5cm thick)
• 1 tbsp olive oil or softened butter
• 150g Gruyère, grated
• 25g Parmesan, finely grated (optional, for extra savoury bite)

How to Make Delia Smith French Onion Soup Recipe

• Prepare the oven: Preheat the oven to 200°C or 180°C fan. Set a shelf in the upper third so the cheese topping melts quickly and colours nicely.
• Start the onions: In a large, heavy-based saucepan or casserole, melt the butter with the olive oil over medium heat. Add the sliced onions, salt, and sugar (if using) and stir well to coat.
• Caramelise (this is the flavour): Cook the onions for 35 to 45 minutes, stirring regularly. You want them deeply golden and sticky, not just softened. If they start catching, lower the heat and add a tiny splash of water to loosen the base of the pan.
• Mix in the thickener: Stir in the chopped garlic for 1 minute, then sprinkle over the flour. Cook for another minute, stirring, so the flour doesn’t taste raw.
• Deglaze: Pour in the wine (if using) and scrape up the browned bits from the bottom. Let it bubble for 2 minutes so the alcohol cooks off and the flavour concentrates.
• Simmer the soup: Add the hot beef stock, thyme, bay leaf, and a good grind of black pepper. Bring to a gentle simmer and cook for 20 to 25 minutes. Taste at the end and adjust salt if needed.
• Bake the bread: While the soup simmers, brush the baguette slices lightly with olive oil or butter. Arrange on a baking tray and bake for 6 to 8 minutes, turning once, until crisp and lightly golden.
• Assemble the bowls: Remove the bay leaf from the soup. Ladle into 6 ovenproof bowls set on a sturdy tray. Float a toast on each bowl, then pile on the Gruyère and a little Parmesan if using.
• Melt and brown: Bake for 8 to 10 minutes until the cheese is melted and bubbling. If you want a deeper golden top, switch to the grill for 30 to 90 seconds, watching closely.
• Cool briefly, then serve: Let the soup stand for 5 minutes before serving. The bowls and cheese will be extremely hot, and that short rest makes it easier (and safer) to eat.

Tips

How do I stop the onions from burning before they caramelise?

Keep the heat at medium or medium-low and stir often, especially once the onions start turning golden. If the base catches, add 1 to 2 tablespoons of water and scrape the pan clean, then continue more gently.

Why does my soup taste bitter?

Bitterness usually comes from scorched onions or too-high heat. Aim for slow browning rather than fast frying, and use a heavy pan to help the onions colour evenly.

How can I make the topping extra bubbly and golden?

Grate the cheese finely (it melts faster), and finish under the grill for a short burst. Keep the bowls on a tray so you can move them in and out quickly.

Can I make this ahead without losing flavour?

Yes, and it often tastes better the next day. Make the soup, cool, and refrigerate. Toast and cheese the bread just before serving so it stays crisp.

Serving Suggestions

• A simple green salad with mustard vinaigrette
• Roast chicken or a baked potato as a hearty main-course pairing
• Extra baguette and salted butter for the table
• A glass of dry white wine, if you used wine in the soup

Storage

Room Temperature

Cool the soup quickly and do not leave it out for more than 2 hours. Because this is stock-based, it’s best refrigerated promptly.

Refrigerator

Store the soup (without the bread and cheese topping) in an airtight container for up to 3 days. Reheat gently on the hob until piping hot, then assemble with fresh toasts and cheese before baking.

Freezing

Freeze the soup base only, for up to 3 months. Defrost overnight in the refrigerator, reheat thoroughly, and finish with freshly toasted bread and cheese for the best texture.

Nutrition

• Calories: 420 kcal
• Carbohydrates: 34 g
• Protein: 18 g
• Fat: 22 g
• Saturated Fat: 12 g
• Sodium: 980 mg

Nutrition values are estimates and will vary depending on your stock, bread, and cheese.

FAQs

Delia Smith French Onion Soup Recipe

0.0 from 0 votes

Course: SoupCuisine: FrenchDifficulty: Medium

Servings

6

bowls

Prep time

15

minutes

Cooking time

1

hour 

Total time

75

minutes

Calories

420

kcal

1

hour 

15

minutes

A rich, deeply flavoured French onion soup with slowly caramelised onions, savoury beef stock, and toasted bread topped with bubbling Gruyère. Comforting, classic, and worth the time.

Ingredients

• 1kg onions, thinly sliced

• 50g unsalted butter

• 1 tbsp olive oil

• 1 tsp fine salt, plus more to taste

• 1 tsp caster sugar (optional, helps browning)

• 2 garlic cloves, finely chopped

• 1 tbsp plain flour

• 150ml dry white wine (optional)

• 1.2 litres hot beef stock

• 2 tsp fresh thyme leaves (or 1 tsp dried)

• 1 bay leaf

• Black pepper, to taste

• 6 slices baguette (about 1.5cm thick)

• 1 tbsp olive oil or softened butter (for the bread)

• 150g Gruyère, grated

• 25g Parmesan, finely grated (optional)

Directions

• Preheat the oven to 200°C (180°C fan). Arrange a shelf in the upper third for toasting the cheesy bread.
• Melt the butter with the olive oil in a large heavy-based pan over medium heat.
• Add the sliced onions with the salt (and sugar, if using). Cook, stirring often, for 35–45 minutes until deeply golden and sweet.
• Stir in the garlic for 1 minute, then sprinkle over the flour and cook for 1 minute more.
• Pour in the wine (if using) and scrape up the browned bits from the base of the pan. Simmer for 2 minutes.
• Add the hot stock, thyme, bay leaf, and black pepper. Simmer gently for 20–25 minutes.
• Toast the baguette slices on a tray for 6–8 minutes, turning once, until crisp and lightly golden.
• Ladle the soup into ovenproof bowls. Float a toast on each bowl, then top generously with Gruyère (and Parmesan, if using).
• Bake for 8–10 minutes until the cheese is melted and bubbling. For extra colour, grill briefly at the end.
• Rest for 5 minutes before serving. The bowls will be very hot.

Notes

• Caramelise the onions slowly for the best flavour. Rushing this step gives a pale, sharp soup.
• Use a heavy pan or cast-iron casserole to prevent scorching and help even browning.
• If your stock is salty, hold back on seasoning until the end.
• No ovenproof bowls? Toast the cheesy bread separately and serve on top of the soup at the table.