French onion soup

Melt the butter and olive oil in a large pan over a medium-high heat. Add the onions and cook, stirring regularly until they begin to soften. Lower the heat and cook until the onions are very sweet and golden-brown. You will need to stir them regularly and it can take one to two hours. Add a tablespoon of water if they begin to stick too much.

Season with salt and pepper. Add the sherry and bring to a simmer, scraping any brown bits as you stir. Leave to simmer for a minute before adding the bay leaf and stock. Leave to simmer for 20 minutes. Taste for seasoning.

Meanwhile, grill the thickly sliced bread on one side. Butter the untoasted side and spread thinly with a little Dijon mustard. Sprinkle the grated cheese on top of the toast.