Whisk flour, eggs, milk, 1/8 litre water and 1 pinch of salt, pass through a sieve and allow to swell for approx. 45 minutes. Peel the asparagus and cut off the woody ends. Put asparagus in boiling salted water and cook for about 20 minutes.
Heat 1 teaspoon of butter in a pan and bake 4 thin pancakes one after the other. Place 1 slice of ham on each pancake, roll up and keep warm. Heat 1/8 litre of water, stir in sauce powder and bring to the boil.
Whisk the remaining butter in small pieces over low heat. Finely chop the chervil and add to the sauce. Add cream and puree with the hand mixer. Drain the asparagus.
Cut ham rolls into slices and arrange on plates with the sauce. Garnish with lemon rose and chervil.