Wash and peel the asparagus and cut off the woody ends. Mix flour, baking powder, 1 pinch of salt, 1 egg and milk. Leave to swell for about 10 minutes
Cook the asparagus in boiling, lightly salted water covered with 1 teaspoon sugar for 15-20 minutes
Stir mineral water into the pancake batter. Heat the clarified butter in portions in a coated pan (approx. 18 cm Ø). From the dough in it one after the other
Bake 4 thin crêpes. Keep warm
In the meantime, whisk 3 egg yolks, cream and 1 pinch of salt with the whisk of the hand mixer in a hot water bath for 6-8 minutes until creamy. Whip the butter into pieces. Season with lemon juice, salt and pepper
Lift out the asparagus (if necessary use the stock for other purposes). Cover the crêpes with 2 slices of ham, roll up loosely and cut into three parts as desired. Serve with asparagus, rest of ham and sauce. If necessary, sprinkle with coarse pepper and garnish with chervil