Boil unpeeled potatoes until tender, about 25-35 minutes. Test with a fork. Drain. When cool enough to handle, peel and press through a potato ricer. Spread onto a baking tray and let cool.
Work potatoes with salt, egg, flour and nutmeg to form a dough. Form into two rolls, just over 1cm in diameter. Cut each roll into 3cm pieces. Form each piece into oval gnocchi and press gently with the prongs of a fork.
Bring a large pot of salted water to the boil. Reduce the heat, so the water is just simmering. Cook gnocchi in simmering water until they float. Remove and drain well.