Cut the butter into pieces to facilitate melting. In a skillet, distribute the butter and sage, and stir over low heat until the butter has melted. Add the cream and cooked gnocchi, and cook over moderate heat, turning gently with a wooden spoon until the gnocchi are coated with sauce and heated through, about 1-2 minutes. Transfer the sauced gnocchi to serving plates, sprinkle with Grana Padano and pepper, top with shaved dry ricotta, and serve immediately.  If dry ricotta is not available, do without—it’s just as good.