French Onion Soup

Method

1. Peel and halve 250 g of onions, then slice them thinly from root to tip, no more than 3 mm thick, so they collapse evenly.
2. Melt 15 g of butter in a small heavy-based saucepan over medium-low heat. Add the onions with a good pinch of salt, stir to coat, and cook uncovered for about 40 minutes, stirring every few minutes and scraping the base, until the onions have shrunk to a soft dark brown jam. If they catch, add a splash of water and stir the brown film back in — that is the flavour of the soup.
3. Sprinkle over 1 tsp of plain flour and stir for 1 minute to cook out the raw taste, then pour in 50 ml of dry white wine. Raise the heat and let it bubble for 2-3 minutes, scraping the pan, until almost fully reduced.