Deep Onion Soup, Gruyere Toast

Method

1. 1

   Start covered 15 min

   Melt the butter with the oil in a wide heavy pot, add the onions, salt and sugar, and put the lid on. Fifteen minutes covered over medium-low sweats the water out and gives the browning something to work with.

2. 2

   Caramelise 45 min

   Lid off, heat at medium-low, and stir every 5 minutes for about 45 minutes. They go pale, then gold, then a deep jammy brown. If they stick, splash in a tablespoon of water and scrape the pot.

3. 3

   Know the colour

   Stop when the onions are the colour of dark toffee and have collapsed to roughly a quarter of what you started with. Pale onions make thin soup and there is no fixing it further down the line.

4. 4

   Deglaze

   Add the thyme and bay, pour in the wine, and scrape every brown patch off the base of the pot. Simmer about 3 minutes, until the wine has almost cooked away.

5. 5

   Simmer 20 min

   Pour in the stock, bring to a bare simmer and cook 20 minutes uncovered. Fish out the bay and thyme stalks, then stir in the sherry vinegar and taste for salt.

6. 6

   Toast and melt

   Toast the baguette slices, float them on the filled bowls and pile the gruyere on top. Under a hot broiler for 2 to 3 minutes, until it bubbles and browns at the edges.

7. 7

   Serve

   Give them 2 minutes before you carry them over. The soup underneath is hotter than it looks and the cheese needs a moment to set into a lid.