Soupe à l'Oignon Gratinée

French onion soup is a study in patience and transformation: raw onions, which can take more than an hour to caramelise properly, collapse into a dark, jammy, intensely sweet base that is then married with beef stock and finished under a grill with a raft of crusty bread and melted Gruyère. Historically a dish of Paris's Les Halles market workers who ate it in the small hours, it is now one of France's most celebrated bistro preparations.

Serves: 4

Ingredients

• 1.2kg (2.6 lb) yellow onions, halved and thinly sliced
• 60g (4 tbsp) unsalted butter
• 1 tbsp neutral oil
• 1 tsp caster sugar
• 200ml (¾ cup) dry white wine or dry vermouth
• 1.2 litres (5 cups) good beef stock
• 2 bay leaves
• 2 sprigs fresh thyme
• Salt and black pepper

Gratin:

• 8 slices baguette, 1cm thick, toasted
• 150g (5½ oz) Gruyère, coarsely grated

Instructions

1. Caramelise onions (55–70 minutes): Melt butter with oil in a large, heavy pot over medium-low heat. Add onions and sugar. Cook, stirring every 5–8 minutes, for 55–70 minutes until onions are deep mahogany brown and reduced to about a quarter of their original volume. Do not rush this step. If they stick, add a splash of water and scrape the base.
2. Deglaze (5 minutes): Increase heat to medium-high. Add wine and scrape up all caramelised bits. Boil until wine is almost completely evaporated, about 3–4 minutes.
3. Simmer soup (20 minutes): Add beef stock, bay leaves, and thyme. Season with salt and pepper. Simmer partially covered for 20 minutes. Discard bay and thyme. Adjust seasoning.
4. Gratin: Preheat grill (broiler) to high. Ladle soup into 4 oven-safe bowls. Float 2 toasted baguette rounds on each. Pile grated Gruyère thickly over the bread and edges of the bowl.
5. Grill (3–4 minutes): Place bowls on a baking tray under the grill until cheese is bubbling and deeply browned in spots.
6. Serve immediately — the bowls will be very hot.

Cook's Notes: The caramelisation cannot be faked or hurried. Blonde onions produce a pale, sweet soup; you want dark, almost burnt-looking onions for the proper depth. Comté can substitute for Gruyère. Use the best beef stock you can find — this is a three-ingredient dish at heart.