This recipe comes, almost completely unmodified, from cooking.com. Since it's cooked in batches, they call for putting the cooked gnocchi in a bowl of melted butter while the others cook, to keep them from sticking together... obviously, this is out, but you could use a LITTLE olive oil or some light margarine instead.
1 lb potatoes
1 3/4 cups all-purpose flour
1 teaspoon salt
1 teaspoon ground nutmeg
Steam potatoes until cooked but firm; peel. Spread flour on a board and sprinkle with 1/2 teaspoon of the salt and the nutmeg. When potatoes are cool, mash without adding any butter or milk. Place potato in a mound in the center of the flour and start incorporating the flour with your hands, little by little, until all but 1/2 cup flour is incorporated. Begin to knead the flour and potato mixture, incorporating the last 1/2 cup of flour. Knead for 5 minutes. Divide the mixture into 3 pieces, roll each piece into a roll 1/2 inch in diameter. Cut each roll into 1 inch pieces, pressing each individual gnocchi with the tines of a fork.
Heat a large amount of water with the remaining 1/2 teaspoon of salt in a large saucepan. When boiling, add gnocchi, one by one. Gently stir with a wooden spoon. After gnocchi come to the surface, allow them to cook for 1 minute more. Remove with a slotted spoon to a dish containing warmed, melted butter. When all are cooked, combine with tomato sauce and serve.