Sauté the crushed garlic cloves in the oil and half of the butter. Before they are browned, take them off the heat and add the thinly-sliced artichokes. Let the artichokes cook slowly, adding a little broth as needed. When the artichokes are cooked, add the rice. Allow it to brown slightly and cook the risotto, gradually adding hot broth. Add salt and pepper to taste. Serve with grated parmesan cheese and the remaining butter.