INGREDIENTS
3 medium onions, 4 tablespoons extra virgin olive oil, 2 tablespoons of flour, 4 tablespoons parmesan cheese, salt.
PROCEDURE
Slice the onions and put them in a pan with oil and a little salt, cook over moderate heat for 5 minutes, add the flour, stirring so that no lumps form, add a liter of hot water and continue cooking for 20 minutes. Heat the oven to 180 degrees, add the Parmesan cheese to the soup and let it gratin in the oven for 15 minutes.