Peel the potatoes, halve or quarter depending on the size and cook in salted water for about 20 minutes. Drain the water and let the potatoes cool.
Press the potatoes through a potato press into a bowl. Add the butter, sweet cream, cornstarch, the 3 egg yolks, nutmeg and pepper and knead everything into a smooth dough. Beat the egg white until stiff and fold in.
Shape the mixture on the floured work surface into a roll and cut into approx. 2 cm thick slices. Heat the clarified butter in a non-stick pan and fry the biscuits over medium heat until golden. This takes about 5 minutes per side.