Peel, wash and roughly grate the potatoes. Stir in egg yolk. Season with nutmeg, salt and pepper
Wash and peel the asparagus and cut off the woody ends. Peel and chop the onion. Clean, wash and slice the mushrooms. Cut the Kasseler into thin strips
Cook the asparagus in approx. 3/4 l boiling salted water covered with some sugar for 15-20 minutes, depending on the thickness
Fry about 12 small, crispy Rösti from the potato mixture in 2 tbsp. hot clarified butter. Lift out the asparagus and keep warm. Measure out 400 ml stock
Fry the onion, mushrooms and smoked pork in 1 tbsp. clarified butter until golden brown. Season everything with pepper. Sprinkle with flour and sweat. Deglaze with cream and asparagus stock while stirring. Bring to the boil and simmer for about 3 minutes. Arrange everything. Garnish with chervil if necessary.