Peel and wash the asparagus and cut off the woody ends briefly. Cook the asparagus in boiling salted water with 1 pinch of sugar for about 20 minutes. Wash the meat and dab dry. Fry all around in hot oil.
Season with salt and pepper and fry for about 15 minutes at medium heat until done. Peel and chop the onions. Fry half of the onions in 1 tablespoon of hot fat. Add wine and let it boil down to half.
Wash, clean, quarter, seed and dice the tomatoes. Drain the mushrooms. Wash basil, pluck leaves from the stalks and, except for some for garnishing, cut into strips.
Fry the rest of the onion and mushrooms in 1 tablespoon of hot fat, season to taste. Add tomatoes and basil and fry. Whisk egg yolk and 2 tablespoons of cream. Heat the remaining fat and sauté the flour in it.
Deglaze with 1/4 l asparagus stock, remaining cream and reduced wine. Bring to the boil, pour through a sieve and alloy with whisked egg. Do not boil any more. Season with salt, pepper and sugar.
Arrange asparagus with meat, mushrooms and sauce on a plate. Garnish with basil.