French Onion Soup with Cheese Gratinee

French onion soup gratinee is the showstopper version of the classic Lyonnais bistro soup. The whole dish lives or dies on the onions, and the rule is patience. Three quarters of a kilo of thinly sliced onions softened slowly in butter and oil is what builds the deep, sweet, almost meaty foundation. Notably, this version asks for golden onions, not deep-browned, which gives a slightly lighter, cleaner soup than American-style versions.

A tablespoon of flour cooked into the softened onions is the discreet thickening move that gives the broth its silky body. Then in goes the beef stock, dry white wine (white, not red, is correct here), and a long covered simmer.

The gratinee step is what makes this special. A slow oven-dried French bread slice goes into each bowl, hot soup is poured over, and finely sliced Gruyere blankets the top. A few minutes under a hot grill turns the cheese into bubbling brown lava with crusty edges where it meets the bowl rim.

Pro Tips

• Slice the onions as uniformly as possible. Uneven cuts cook unevenly and you’ll have raw bits in the finished soup.
• Use ovenproof bowls. Standard ceramic can crack under the broiler.
• Skim the soup as it simmers. Cleaner foam makes a clearer, more elegant broth.
• Drying the bread in a low oven instead of toasting makes it crisp without browning, so it holds shape under the soup.

Variations

• Use veal stock for a more refined, classically French version.
• Add a splash of cognac or sherry at the end for warmth and depth.
• Mix Emmental and Gruyere for a cheese cap with both stretch and bite.