French onion soup, or soupe à l’oignon, is one of the great dishes of Paris – humble, comforting and full of depth. Traditionally, it was little more than water poured over stale bread crusts with a single onion added, left to simmer slowly in rural kitchens. But in the city, it became something else: the go-to 4am pick-me-up for butchers and purveyors at Les Halles, the legendary Paris produce market.

In my version, I take the time to caramelise the onions properly, then deglaze with port and dry white wine, adding a rich veal stock for body. I finish it with a spoonful of crème fraîche enriched with egg yolk, gruyère croutons on top and end with a sprinkle of parsley. It’s deeply nostalgic – and deeply satisfying. Add it to your winter soup rotation.

Ingredients

Serves 4

• 100 g (3 ½ oz) salted butter
• 1.6 kg (3 ½ lb) onions, sliced
• 2 small garlic cloves, sliced
• 2 thyme sprigs
• 1 large fresh bay leaf
• 2 egg yolks
• 75 g (2 ¾ oz/ 1/3 cup) crème fraîche
• 1/2 baguette, cut into 1 cm (½ in) slices
• 80 g (2 ¾ oz) gruyère, grated
• 80 ml (2 ½ fl oz/1/3 cup) port
• 80 ml (2 ½ fl oz/1/3 cup) dry white wine
• 1 litre (34 fl oz/4 cups) veal stock
• sea salt and freshly ground black pepper, to taste
• finely chopped flat-leaf (Italian) parsley, to serve

Method

1. Melt the butter in a large saucepan over medium heat, then add the onions, garlic, thyme and bay leaf. Cook for 40 minutes, stirring occasionally, until the onions are caramel in colour. Discard the herbs.
2. Meanwhile, in a small bowl, whisk the egg yolks into the crème fraîche until well combined. Cover and place in the refrigerator until ready to serve.
3. Preheat the oven grill (broiler) to 180°C.
4. To make the croutons, place the baguette slices on a baking tray. Cook under the grill for 1 minute, or until lightly toasted, then turn and sprinkle a spoonful of gruyère over each slice and return to the grill for 2–3 minutes, or until the cheese is melted and golden. Remove from the oven and set aside.
5. Add the port and white wine to the onions and boil, stirring, for 30 seconds to deglaze the pan (this will ensure all of the flavours are released into the soup). Cook the soup for two minutes more, or until slightly reduced, then stir in the veal stock and bring to the boil. Season with salt and pepper, to taste, then remove the pan from the heat.
6. To serve, pour the egg yolk – crème fraîche mixture into bowls, then ladle the onion soup on top. Place a gruyère crouton on top of each bowl and garnish with parsley. Serve with extra croutons if desired.

You can find this and more recipes in Plat Du Tour by Guillaume Brahimi. This dish and other Guillaume classics will feature on the menu at Bistro Guillaume's upcoming pop up at Baker Bleu this August.