Cook the potatoes until soft, peel them and press them while still hot through the potato press onto a lightly floured baking board. Salt lightly, add the egg and knead with the flour, using just enough flour until the dough no longer sticks to your fingers. Take an egg-sized amount each and shape into a roll (approx. 1 1/2 cm in diameter). Cut off pieces approx. 2 cm long and roll them over the inside of a fork with your thumb.
Soak the gnocchi in plenty of boiling salted water and let stand for a few minutes (turn down the temperature). As soon as the gnocchi float on top, lift them out with a slotted spoon and drain well.
Toss in a pan with a little butter and serve with any sauce.