Peel and slice all the yellow onions very thinly. This part takes time but it is very important.

Melt the butter and oil in your large pot. Add the onions and cook them on low heat.

Stir the onions every few minutes for one hour. They should turn a very deep golden brown color.

Add the white wine to the dark brown onions. Scrape the bottom of the pot to get flavor.

Pour in the beef stock and add the herbs. Let the soup simmer softly for thirty minutes today.

Take out the thyme sprigs and the bay leaf. Add more salt and pepper if you like it.

Cut the baguette and toast it in the oven. The bread must be very dry and quite crunchy.

Pour soup into bowls and top with toasted bread. Add lots of cheese and broil until it bubbles.