- 1kg onions – preferably large Spanish onions
- 30g butter
- 1 heaped tbsp flour
- 250ml dry white wine
- 1½ litres of beef, chicken or vegetable stock
- 1 bay leaf
- 1 sprig of thyme
- Balsamic vinegar, to taste (optional)
- Brown sugar, to taste (optional)
- Baguette, cut into 12 thin slices
- 150g gruyere or similar cheese, grated
Slice the onions finely – don’t worry if you have a mountain, they will collapse and reduce once you begin to cook them. Melt the butter in a large sauté or frying pan and add the onions, along with a good pinch of salt and a grind of black pepper.
Cook the onion gently, stirring regularly, for anything between 45 mins and 1 hour (larger quantities will take a little longer). The onions will collapse and become almost creamy – the idea is to caramelise but never burn them. The colour and savoury depth of the soup is all down to patience here, so do allow the flesh to become a really deep gold.
Add the flour to the pan and stir it into the onions, cooking it for 2 mins. Slowly pour in the wine, stirring all the time, and allow the pan to come up to the boil. Tip in the stock – I love the richness of a good beef stock, but that’s up to you. Add the herbs and simmer for about 15 mins. Balance the soup with salt, pepper, balsamic vinegar and even a little sugar. Place slices of baguette on an oven tray and top with the grated cheese. Grill the croutons for 2 mins, until the cheese is melting and bubbly. Serve the hot soup in bowls, topped with a pair of croutons.