Bring a large pot of salted water to a boil. Add the pasta and cook until tender, about 8 to 10 minutes. Meanwhile, crumble Gorgonzola in the top of a double boiler. Whisk in broth, Madeira and heavy cream, garlic clove and cook uncovered for 3 to 4 minutes or until the cheese has melted. Remove garlic clove. Drain the pasta, pat it dry and spoon into a deep dish. Top with spoonfuls of sauce and top with walnuts.