Peel the potatoes and boil them until softened. Blend them or crush them with a fork. Add egg yolks, salt, black pepper, nutmeg and flour.
Mix well and form balls with wet hands. Boil them in salted water. Take them out and drain them.
Mash the tomatoes and saute them on low heat until thickened. Pour in the olive oil and saute for another 3 min. Pour it out into a tray.
Arrange the potato balls on top and sprinkle with grated cheese. Bake at 374°F (190°C) until the cheese melts.