Delia Smith French Onion Soup Recipe

This classic French onion soup is deeply savoury, rich, and comforting, with beautifully caramelised onions in a flavourful broth. Topped with crisp toasted bread and bubbling melted cheese, it offers a perfect balance of sweetness and depth. It is a moderately easy recipe that rewards patience during the slow cooking of onions. Allow around 1 hour 15 minutes from start to finish for the best results.

Ingredients

For the soup base

50g unsalted butter
1 tbsp olive oil
1kg onions, thinly sliced
1 tsp sugar
2 cloves garlic, crushed
1 tbsp plain flour
150ml dry white wine
1.2 litres good-quality beef stock
1 bay leaf
Salt and freshly ground black pepper

For the topping

4–6 slices baguette
150g Gruyère cheese, grated

How to Make Delia Smith French Onion Soup Recipe

Prepare the base: Melt the butter with the olive oil in a large heavy-based pan over low heat. Add the sliced onions and cook gently for 10 minutes until softened.
Caramelise the onions: Sprinkle in the sugar and continue cooking over low to medium heat for 25–30 minutes, stirring occasionally, until the onions are deeply golden and caramelised.
Add garlic and flour: Stir in the crushed garlic and cook for 1 minute. Add the flour and stir well to coat the onions evenly.
Deglaze with wine: Pour in the white wine and let it bubble for 2–3 minutes, scraping up any bits from the bottom of the pan.
Add stock and simmer: Stir in the beef stock and add the bay leaf. Bring to a gentle simmer and cook for 20 minutes. Season to taste with salt and pepper.
Prepare the bread: Preheat the grill. Toast the baguette slices until golden on both sides.
Assemble the soup: Ladle the soup into ovenproof bowls, place toasted bread on top, and sprinkle generously with grated Gruyère.
Grill until golden: Place under a hot grill until the cheese is melted, bubbling, and lightly golden. Serve immediately.

Tips

How do I get deeply caramelised onions?

Cook them slowly over low heat and avoid rushing. Stir occasionally and allow natural sugars to develop for the best flavour.

Can I use a different cheese?

Yes, Comté or mature Cheddar can be used, but Gruyère gives the most authentic taste and melt.

What stock works best?

Beef stock gives a rich, traditional flavour, but a good vegetable stock can be used for a lighter version.

How do I avoid soggy bread?

Toast the bread well before adding it to the soup so it holds its structure under the cheese.

Serving Suggestions

Serve with a simple green salad
Pair with roasted meats for a fuller meal
Enjoy with a glass of dry white wine
Serve as a starter for a classic French-style dinner

Storage

Room temperature

Do not leave the soup out for more than 2 hours after cooking.

Refrigerator

Store the soup (without bread and cheese) in an airtight container for up to 3 days. Reheat gently on the hob.

Freezing

Freeze the soup base for up to 3 months. Defrost fully before reheating and adding fresh toppings.

Nutrition

Calories: 320 kcal
Carbohydrates: 28g
Protein: 12g
Fat: 18g
Saturated Fat: 9g
Sodium: 780mg

These values are approximate and may vary depending on ingredients used.

FAQs

Can I make French onion soup in advance?

Yes, the soup base can be made a day ahead and reheated. Add the bread and cheese topping just before serving.

Can I make this recipe vegetarian?

Yes, simply replace the beef stock with a rich vegetable stock for a vegetarian version.

What onions are best for this soup?

Brown or yellow onions work best as they caramelise beautifully and provide a balanced sweetness.

Can I skip the wine?

Yes, you can replace the wine with extra stock and a small splash of vinegar for acidity.