Wash spinach and remove tough stems. Plunge briefly into boiling water. Cook only until limp. Rinse with cold water. Drain, squeeze dry, and chop. Melt butter in a small skillet. Add spinach and cook until dry (it will begin to stick to the bottom of the pan). Blend in the ricotta cheese. Heat thoroughly and empty into a bowl. Stir in eggs, flour, Parmesan cheese, salt, pepper, and nutmeg. Cover with foil and chill until firm – about 1 hour. Bring 6 quarts of salted water to a boil. Take spinach mixture up by tablespoonfuls and shape gently into balls. Roll in flour. Drop 5 or 6 at a time into the boiling water. Cook until they rise to the top and are slightly puffed. Remove with a slotted spoon and drain on paper toweling. Serve with Tomato and Cream Sauce.