Mary Berry French Onion Soup Recipe

French onion soup is the most satisfying thing patience can produce. Onions cooked slowly — genuinely slowly, forty-five minutes to an hour — until they collapse into a deeply sweet, mahogany-coloured mass.

A rich beef stock added and simmered until reduced and intense. Ladled into bowls, topped with a croûte of toasted baguette, and covered in melting, bubbling Gruyère that goes golden and slightly charred under the grill.

When it is right, it is one of the most extraordinary things a bowl can contain.

Mary Berry’s French onion soup recipe follows the classic method faithfully — no shortcuts, no rushing, no substituting sweet caramelised onions with quickly softened ones. The patience is the recipe.

Every minute the onions spend in the pan deepens their sweetness, darkens their colour, and builds the complex, slightly bitter, deeply savoury foundation that makes this soup what it is.

The One Rule of French Onion Soup

The onions must be properly caramelised. Not softened. Not golden. Properly, deeply, mahogany caramelised — collapsed, almost jammy, sweet and dark.

This takes forty-five minutes to one hour of cooking over a medium-low heat. There is no shortcut. There is no way to rush caramelisation without burning the onions. The patience is non-negotiable and completely worth it.

Recipes that claim to produce French onion soup in thirty minutes are not making French onion soup. They are making onion soup — a different and considerably less interesting thing.

Ingredients for Mary Berry French Onion Soup

For the Soup

• 75g unsalted butter
• 1 tbsp olive oil
• 1.5kg onions (approximately 6 large), thinly sliced
• 1 tsp caster sugar
• 3 garlic cloves, crushed
• 2 tbsp plain flour
• 200ml dry white wine
• 1 litre good quality beef stock
• 200ml water
• 2 bay leaves
• 4 sprigs fresh thyme
• 1 tsp Worcestershire sauce
• Salt and freshly ground black pepper

For the Gruyère Croûtes

• 1 baguette, cut into 1.5cm slices (2–3 slices per bowl)
• 175g Gruyère cheese, finely grated
• 1 tbsp Dijon mustard (optional — spread thinly on each croûte before cheese)

How to Make Mary Berry French Onion Soup — Step by Step

Step 1 — Caramelise the Onions

Melt the butter with the olive oil in a very large, heavy-based pan over a medium heat. Add all the sliced onions and the caster sugar. Stir to coat everything in the butter.

Cover the pan and cook for 15 minutes over medium heat, stirring occasionally, until the onions have started to soften and collapse.

Remove the lid. Reduce the heat to medium-low and continue cooking, stirring every five to eight minutes, for a further 30 to 40 minutes until the onions are completely collapsed, deeply golden-brown, and almost jammy in consistency. The onions will reduce to about a quarter of their original volume. Season with salt.

If the onions start to stick or catch at any point, add a tablespoon of water and stir to release them. This deglazed water carries flavour back into the onions.

Step 2 — Add the Garlic and Flour

Add the crushed garlic and cook for two minutes. Sprinkle over the flour and stir for one to two minutes to cook the flour through.

Step 3 — Deglaze and Build the Soup

Pour in the white wine. Let it bubble vigorously for two to three minutes, stirring to scrape up every last bit of caramelised onion from the base of the pan. This is the most flavourful moment of the entire recipe — do not rush the deglazing.

Add the beef stock, water, bay leaves, thyme, and Worcestershire sauce. Bring to the boil, then reduce to a gentle simmer. Cook uncovered for 20 to 25 minutes until the soup has reduced slightly and the flavours have developed. Remove the bay leaves and thyme sprigs. Taste and season generously.

Step 4 — Make the Croûtes

While the soup simmers, preheat your grill to high. Arrange the baguette slices on a baking tray. Toast under the grill for two to three minutes per side until golden and crisp on both sides.

Spread each croûte with a thin layer of Dijon mustard if using. Set aside.

Step 5 — Assemble and Grill

Preheat your grill to its highest setting.

Ladle the hot soup into ovenproof soup bowls — they must be ovenproof, as they go under the grill. Place two to three croûtes on top of each bowl of soup. Pile the grated Gruyère generously over the croûtes — be very generous. The cheese should completely cover the croûtes and slightly overhang the edges of the bowl.

Place the bowls on a baking tray and slide under the hot grill for three to four minutes until the cheese is completely melted, bubbling, and deeply golden with slightly charred edges. Watch constantly — the cheese goes from perfect to burnt very quickly.

Step 6 — Serve

Serve immediately — the soup must arrive at the table while the cheese is still bubbling. Use oven gloves and warn guests that the bowls are extremely hot.

My Top Tips For Mary Berry French Onion Soup

The onions need a full forty-five minutes. Set a timer if it helps — and check it every five to eight minutes rather than staring at it. The onions go through several stages: softening, collapsing, turning golden, turning amber, then turning that deep mahogany brown that signals they are ready. Each stage builds on the last. Do not stop early.

Use the highest quality beef stock you can find. The soup is mostly stock once the onions are done. Fresh beef stock from a butcher or good quality fresh stock from a supermarket chiller cabinet is significantly better than stock made from a cube.

Deglaze properly. When the wine goes in and bubbles up, scrape every caramelised bit from the base and sides of the pan into the liquid. These bits are pure concentrated onion flavour.

Use ovenproof bowls. The bowls go under the grill. They must be able to withstand the direct heat. French onion soup crocks — the classic heavy ceramic bowls — are ideal.

Be very generous with the Gruyère. A thin layer of cheese on French onion soup is a disappointment. The cheese should completely cover the croûtes and be thick enough to bubble and develop colour. Use all 175g for four bowls.

Serve immediately. The cheese is at its finest the moment it comes from under the grill — melted, bubbling, slightly charred. Do not leave it to cool. French onion soup waits for nobody.

Serving Suggestions

On its own with nothing alongside — it is a complete meal in a bowl. As a dramatic dinner party starter in individual ovenproof bowls. With a simple green salad as a light lunch.

How to Store Mary Berry French Onion Soup

The soup (without croûtes): Store in an airtight container for up to 4 days. Reheat gently on the hob. Make fresh croûtes and add the cheese topping when reheating.

In the freezer: Freeze the soup without the croûtes for up to 3 months. Defrost overnight in the fridge and reheat gently.

Mary Berry French Onion Soup Recipe

Mary Berry's French onion soup is a deeply rich, dark broth with sweet caramelised onions and a gruyère croûte

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Prep Time 15 minutes mins

Cook Time 1 hour hr 20 minutes mins

Total Time 1 hour hr 35 minutes mins

Servings: 4 Portions

Course: Soup

Cuisine: British

Calories: 490

Ingredients Method Notes

Ingredients

  

• Soup:
• 75 g unsalted butter
• 1 tbsp olive oil
• 1.5 kg onions thinly sliced
• 1 tsp caster sugar
• 3 garlic cloves crushed
• 2 tbsp plain flour
• 200 ml dry white wine
• 1 litre beef stock
• 200 ml water
• 2 bay leaves 4 thyme sprigs
• 1 tsp Worcestershire sauce
• Salt and pepper
• Gruyère Croûtes:
• 1 baguette sliced 1.5cm thick
• 175 g Gruyère finely grated
• 1 tbsp Dijon mustard optional

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Method

 

1. Melt butter and oil in a large heavy pan. Add onions and sugar. Cover and cook 15 minutes over medium heat. Remove lid — cook over medium-low heat 30–40 more minutes, stirring every 5–8 minutes, until deeply mahogany brown and almost jammy. Season with salt.
2. Add garlic — 2 minutes. Sprinkle over flour — stir 1–2 minutes.
3. Add wine — bubble vigorously 2–3 minutes, scraping base. Add stock, water, bay leaves, thyme, and Worcestershire sauce. Simmer uncovered 20–25 minutes. Remove bay leaves and thyme. Season.
4. Toast baguette slices under a hot grill on both sides. Spread with mustard if using.
5. Ladle hot soup into ovenproof bowls. Top with 2–3 croûtes per bowl. Cover generously with Gruyère.
6. Grill on highest setting 3–4 minutes until cheese is completely melted, bubbling, and deeply golden. Serve immediately.

Notes

The onions need 45 minutes minimum — patience is the entire recipe.

Use the best beef stock available — it is the backbone of the soup.

Deglaze thoroughly with the wine — those caramelised bits are pure flavour.

Use ovenproof bowls — they go under a hot grill.

Be very generous with the Gruyère — a thin layer disappoints.

Serve immediately — the cheese is at its finest the moment it comes from the grill.

Freeze soup without croûtes for up to 3 months.

Frequently Asked Questions

Can I use vegetable stock instead of beef?

You can but the result is significantly less rich and less complex. If making a vegetarian version, use a very good quality vegetable stock and add a tablespoon of dark soy sauce for depth and colour.

Can I use a different cheese?

Gruyère is the classic choice and gives the best result — it melts beautifully and has the right flavour. Emmental is the closest substitute. Mature Cheddar works but gives a different, less elegant result.

How do I know the onions are properly caramelised?

They should be reduced to about a quarter of their original volume, deeply mahogany brown in colour, soft and almost jammy in texture, and sweet rather than sharp when you taste them. If they taste even slightly sharp or raw, they need more time.

Can I make French onion soup the day before?

Yes — the soup itself improves overnight. Store in the fridge and reheat before serving. Make the croûtes and add the cheese fresh when serving.

Can I add red wine instead of white?

Yes — red wine gives a darker, more robust soup. Use the same quantity and the same method.