Peel, wash and halve the potatoes and cook in salted water for 15-20 minutes. Cut off woody asparagus ends, wash asparagus. Peel white asparagus. Cut the asparagus diagonally into pieces.
Bring 1 litre of water to the boil in a saucepan. Salt it. Steam white asparagus in a closed pot for about 10 minutes. Add green asparagus to the pot after about 5 minutes of cooking time. Drain the asparagus on a sieve, collecting the asparagus water.
Melt the fat in a pot. Stir in flour, add asparagus water while stirring and bring to the boil. Add cream and heat slowly over medium heat. Rinse chicken filet, dab dry and cut into approx. 12 strips.
Thread about 3 strips each onto a wooden skewer. Finely grate the Parmesan cheese. Wash the rocket, dab dry and chop very finely, except for a few leaves for garnishing. Add the rocket and Parmesan cheese to the sauce and whip with a blender.
Crush the pink berries between your fingers and season the sauce with them. Season to taste with salt. Warm the potatoes and asparagus in the sauce. Heat oil in a pan. Fry chicken skewers in it until golden brown all around, season with salt and pepper and cook on medium heat for about 5 minutes.
Arrange ragout on deep plates, cover with skewers and garnish with rocket leaves.