The cheesy crust on top of this soup is what makes the French staple difficult to resist.
- 2 tbsp olive oil
- 50 g butter
- 3 brown onions, thinly sliced
- 3 red onions, thinly sliced
- 3 white onions, thinly sliced
- ½ tsp soft brown sugar
- 250 ml (1 cup) dry white wine
- 1 litre (4 cups) good-quality chicken stock
- 1 bay leaf
- 2 tbsp Cognac, dry vermouth or dry sherry
- 200 g (1½ cups) grated Gruyère cheese
- Sourdough baguette, cut into 12 thick slices
- 2 tbsp olive oil
Oven temperatures are for conventional; if using fan-forced (convection), reduce the temperature by 20˚C. | We use Australian tablespoons and cups: 1 teaspoon equals 5 ml; 1 tablespoon equals 20 ml; 1 cup equals 250 ml. | All herbs are fresh (unless specified) and cups are lightly packed. | All vegetables are medium size and peeled, unless specified. | All eggs are 55-60 g, unless specified.
Heat the olive oil and butter in a large heavy-based saucepan over medium heat. Add the onions and stir to coat in the oil and butter mixture. Reduce the heat to low, then cover and cook for 30 minutes, stirring occasionally.
Stir in the sugar and wine. Cover and cook for a further 30 minutes, stirring occasionally, until the onions are very tender.
Remove the lid and continue to cook, stirring, for another 5–10 minutes, until the onions begin to caramelise and become an even golden brown.
Add the stock and bay leaf, then simmer for another 30 minutes. Meanwhile, preheat the oven to 160°C. To make
the croutons, lightly brush both sides of each slice of bread with olive oil and place on a baking tray. Bake for 10 minutes on each side, until crunchy and deep golden brown.
Increase the oven temperature to 200°C. Remove the bay leaf from the soup. Stir in the Cognac, then taste
and season with sea salt flakes and freshly ground black pepper.
Pour a small ladle of soup into six ovenproof soup bowls. Add a crouton and a sprinkling of Gruyère cheese. Ladle in the remaining soup, then add another crouton to each bowl and a thick layer of cheese.
Place the bowls on a baking tray and carefully transfer to the oven. Bake for about 5 minutes, or until the soup is bubbling hot and the cheese has formed a golden crust.
Allow to stand for a few minutes before serving, as the soup and bowls will be extremely hot.
This recipe is from Low & Slow (Smith Street Books).