Artichoke soup

Instructions
Remove the thorns and hard leaves of artichokes, wash and put them to soak for half an hour in water acidulated with lemon. Drain it by removing as much water as possible, then cut into slices. Fry a finely chopped onion in butter, add the sauteed and peppered artichokes and cook for a few minutes. Cover with hot broth (one liter plentiful). Complete cooking (the artichokes should be tender and dish up directly in holsters on the edges of which you will have prepared bread croutons browned in butter. Serve Grana aside.