Wash the asparagus, peel generously, cut off the woody ends. Wash the potatoes thoroughly.
Boil the potatoes in water for about 20 minutes. Cook the asparagus in boiling salted water covered with 1 teaspoon sugar for 12-15 minutes.
Wash parsley, shake dry and chop finely. Dab meat dry. Heat the oil in a pan and fry the medallions in it over high heat on each side for about 2 minutes. Season with salt and pepper.
In the meantime heat butter and let it froth up once. Melt the truffle butter in it. Drain potatoes and mix with parsley. Lift out the asparagus and drain well. Serve with meat and parsley potatoes.
Pour half of the butter mixture over it and add the rest.