Heat the olive oil slightly in a non-stick frying pan, and immediately add the thinly sliced onions. Let them cook over a moderate heat, with the lid on the pan, for about half an hour. Add 1 or 2 spoonfuls of water if necessary, to keep them from burning: onions can be “difficult”. Grease a heatproof dish with 2 tablespoons of olive oil, and spread out 1 or 2 spoonfuls of the cooked onions in the bottom. Cover with some of the toasted bread, 2 ladles of broth, more onions and a good sprinkling of grated pecorino cheese. Repeat this layering with the rest of the ingredients and finish off with grated cheese. Put the dish in a preheated oven, at 180 °C, until the top is well browned. Leave the soup to “rest” for at least 15 minutes before serving. This soup is known as Carabaccia in Florence; the name comes from the Greek “Karabos”, meaning a shell-shaped boat. From idea of the shell it passed on to a soup terrine, and then the soup itself. It is mentioned in a cookery book that dates back to the 1500s, with the name of Carabazada (in those days crushed almonds, cinnamon, sugar and vinegar were added to the onions). Florentine Carabaccia can be considered the ancestor of all “modern” onion soups, including the famous French “soupe à l’oignon”.