Butter, chopped fresh sage, freshly grated parmesan
Force the mashed potatoes through a sieve or potato ricer into a large bowl. Make a well in the center, break in the eggs, and beat lightly. Add one cup of the flour, nutmeg, and salt and pepper if necessary (if the mashed potatoes were well-seasoned, more salt and pepper probably is not required <grin>), and mix with the fork. Add enough additional flour to make a moist, but firm dough - like home made play dough in consistency.
Turn the dough out onto a lightly floured surface, and knead and shape it into a ball. Divide the ball into 6 pieces.
Put a large pot of water onto boil, and when it is boiling salt it fairly heavily - about a heaping tablespoon.
Roll the dough pieces into logs, and cut into about 3/4 inch pieces. Pick up each piece, and press it onto a fork with your thumb, rolling it off. See gnocchi-shaping pictures.
Drop the formed gnocchi into the boiling water, and cook them until they float, stirring once or twice to make sure they don't stick to the bottom of the pot. Drain them, and, if you are not going to eat them right away, rinse with cold water, drain again, and arrange in a single layer on a wax paper lined sheet pan. When they're cool, you can freeze them or cover and refrigerate to cook within a few days or hours.To eat the gnocchi right away, drain, but don't rinse them, and drop them into a warm pan with melted butter and chopped sage, toss well, and serve with freshly grated parmesan. They're also good with tomato sauce, or in a gratin.