For the crespelle, mix flour, 1/2 teaspoon salt and 1/8 l milk until smooth. Stir in 3 eggs and oil, cover and let it swell for about 20 minutes.
Wash the asparagus, peel generously, cut off the woody ends. Cook in boiling salted water covered with 1 tsp. sugar for about 12 minutes. Lift out the asparagus and drain.
Heat some butter in a pan. Stir mineral water into the dough. Put about 1/8 of the dough into the pan and bake a thin, golden brown pancake while turning. Bake 7 more crespelle one after the other.
Preheat oven (electric cooker: 200°C/circulating air: 175°C/gas: level 3). Place 1 slice of ham and 3-5 asparagus spears on each crespelle, roll up. Put them into a greased casserole dish.
Whisk 3 eggs, cream and 5 tablespoons of milk. Season with salt, pepper and nutmeg, pour over the crespelle. Grate cheese over it. Bake in a hot oven for about 30 minutes. Garnish with chervil.