Name: Soupe à l’oignon gratinée
Prep time: 25 min
Cook time: 85 min
Total time: 110 min
Yield: 6 ovenproof bowls, about 450 ml each
Cuisine: French
Ingredients: 1200 g yellow onions — peeled and thinly sliced; 60 g unsalted butter; 25 g plain wheat flour; 200 ml dry white wine — contains sulphites; 1500 ml low-sodium beef stock — prepared with celery; 6 g fine salt; 2 g black pepper — freshly ground; 300 g baguette — cut into 12 slices; 240 g Gruyère cheese — coarsely grated

Soupe à l’oignon gratinée — shown in a cooking pot

Prep 25 minutes

Cook 85 minutes

Total 110 minutes

Yield 6 ovenproof bowls, about 450 ml each

Ingredients ↓

Introduction and overview

Soupe à l’oignon gratinée — French onion soup gratinée

Soupe à l’oignon gratinée is defined by patience with the onions and by the contrast between broth below and gratinéed bread and cheese above. The onions are not simply softened: they cook slowly until deep amber-brown, building the roasted sweetness and savoury depth that a thin, pale onion broth cannot supply. Dry white wine then lifts the browned residue from the pot before beef stock turns it into a soup.

The topping is a separate piece of the technique. Toasted baguette gives the cheese a platform and slows immediate collapse into the broth; grated Gruyère then melts and browns under strong top heat. The goal is a bubbling, browned cap over a still-fluid onion soup, not a thick cheese sauce stirred through the pot.

Because each portion is finished in an individual heatproof bowl, the service itself needs care. The bowls sit on a stable rimmed tray for gratinating and stay dangerously hot after they leave the grill. This is one dish where the practical burn warning matters as much as the visual drama of the browned cheese.

Keys to a deep gratinée

Give the onions the full browning time.
Reduce the wine before adding stock so it does not dominate.
Gratinate only in bowls explicitly rated ovenproof.

Ingredients

Soup

1200 g yellow onions — peeled and thinly sliced
60 g unsalted butter
25 g plain wheat flour
200 ml dry white wine — contains sulphites
1500 ml low-sodium beef stock — prepared with celery
6 g fine salt
2 g black pepper — freshly ground

Gratin topping

300 g baguette — cut into 12 slices
240 g Gruyère cheese — coarsely grated

Method

Directions

Brown the onions deeply. Melt the butter in the heavy pot, add the onions and salt and cook for 45 minutes over medium-low heat, stirring more often as they darken. The onions are soft, reduced in volume and deep amber-brown with no black burnt patches.
Cook the flour. Sprinkle over the flour and stir for 2 minutes. The flour is evenly absorbed and no dry white patches remain.
Deglaze with wine. Pour in the wine, scrape the pot base thoroughly and reduce for about 5 minutes. The browned residue has dissolved into the liquid and the wine is reduced by roughly half.
Simmer the soup. Add the stock and pepper and simmer uncovered for 20 minutes at about 90–95 °C. The broth tastes integrated rather than sharply wine-forward and the onions remain distinct strands.
Toast the bread. Toast the baguette slices at 180 °C for 8 minutes. The bread surfaces are dry and pale golden while the centres remain firm enough to float.
Assemble the bowls. Set six 450 ml ovenproof bowls on a rimmed tray, divide in the hot soup, then top each bowl with two bread slices and 40 g Gruyère. The bread covers most of the surface and the cheese is distributed evenly over it.
Gratinate safely. Place the tray under high top heat for about 5 minutes. The cheese is fully melted, bubbling and browned in patches without black scorching.

Serving

Practical

Serving

Serve immediately on heatproof underplates and warn diners that the bowl and cheese are extremely hot.

Make-ahead

Cook the onion soup base up to 2 days ahead, cool promptly and refrigerate. Toast the bread and grate the cheese separately. Assemble and gratinate only for service.

Storage and reheating

Refrigerate the soup base or leftovers within 2 hours and use within 3–4 days. Reheat the soup to 74 °C before topping and gratinating. A fully assembled leftover bowl will have softer bread.

Substitutions

Chicken stock gives a lighter result than beef stock but keeps the method intact. A comparable firm melting cheese can work, but the flavour will differ from Gruyère.

Troubleshooting

Pale, thin soupThe onions were stopped before deep browning or the broth was not simmered long enough. Continue browning patiently and finish the full simmer.
Burnt cheese before hot soupThe bowl entered the grill too cool. Reheat the soup until very hot before assembling so the short gratin stage is enough.

Nutrition per serving

Serving size1 ovenproof bowl, about 450 ml (1 of 6)
Calories518 kcal
Carbohydrate48.8 g
Protein23.0 g
Fat23.4 g
Fibre4.9 g
Sodium1235 mg

Allergens and food safety

Allergens: Milk, Gluten (wheat), Celery, Sulphites.

Hot soup and gratin bowls are burn hazards. The stock contains celery; the bread contains gluten; the cheese contains milk; wine contributes sulphites. Refrigerate leftovers within 2 hours and reheat to 74 °C.

FAQ

How dark should the onions be?

Aim for deep amber-brown throughout, not black edges. The depth of the soup comes from this stage.

Can the bowls be gratinéed in advance?

No. Keep soup, toast and cheese separate and finish under top heat immediately before serving.

Closing

Result: Deep onion broth under a bubbling browned Gruyère crust.
Decisive technique: Brown the onions patiently, then gratinate only when the soup is already hot.

Soupe à l’oignon gratinée — French onion soup gratinée

Keys to a deep gratinée

Ingredients

Soup

Gratin topping

Method

Practical

Serving

Make-ahead

Storage and reheating

Substitutions

Troubleshooting

Nutrition per serving

Allergens and food safety

FAQ

How dark should the onions be?

Can the bowls be gratinéed in advance?

Closing

French Recipes

Soupe au fromage

Soupe au pistou

Soupe corse