100g unsalted butter
10 large onions, sliced
750ml dry white wine
sea salt and freshly ground black pepper
1/4 cup cognac
2 litres veal or rich chicken stock
1 fresh bay leaf
1/2 loaf French bread, sliced into 3cm-thick rounds
1+1/2 cups grated gruyère cheese
You can cook this soup in advance and refrigerate but reheat before putting in the oven.
In a large heavy-based saucepan, melt the butter.
Add the onions and sauté, stirring occasionally, for around 35 minutes or until they have completely softened and browned.
Add the white wine, some salt and black pepper an boil until the wine has reduced to 1 cup.
Add the cognac and cook a further 2 minutes.
Add the veal or chicken stock and bay leaf, bring to the boil, then simmer for 15 minutes.
While the soup is cooking, bake the bread slices in a moderate oven (180°C) until dry (around 15 minutes).
Taste and season the soup then ladle into heatproof soup bowls.
Top with the bread slices and a good handful of gruyère cheese.
Place on a tray in the oven until the soup is bubbling and the cheese is golden brown.