Peel the onions and cut them into thin rings. Warm the butter in a pot and lightly saute the onions in it. Sprinkle on flour and stir, then pour on the vegetable stock. Bring to a boil, lower the temperature and cover. Simmer for 30 minutes. Add salt and pepper to taste. Slice the bread and lightly toast. Grate the cheese in the food processor and serve with the soup.

Encourage people to prepare as follows:

In a bowl of soup, place a slice of bread on top, then sprinkle cheese over it. Let the bread soak up the soup and get soft before eating.