For the Erdäpfeltascherln with truffles, knead all ingredients into a smooth, pliable dough. Wrap in cling film and leave to rest in a cool place.
Meanwhile, cook potatoes in their skins until soft, peel while still hot and press through a potato press. Allow to cool slightly. Chop truffles into small cubes and mix with cream cheese, truffle oil, egg yolk, Parmesan cheese and a pinch of salt into the potato mixture.
Roll out the pasta dough thinly on a floured work surface and cut out slices with a round cutter or glass (approx. 8 cm Ø). Spread a little potato filling on each, brush the edge with egg yolk and fold the dough into a small bag. Press down the edge well.
Bring salted water to a boil, add noodles and cook until lightly boiling, about 10 minutes. Lift out and drain. Arrange the Erdäpfeltascherln with truffles on preheated plates and drizzle with some warmed veal jus.