Bring the asparagus skins and sections to the boil in about 1 3/4 litres of water and simmer for about 15 minutes. Drain and collect the asparagus water. Melt the fat in a pot. Sweat flour in it.
Deglaze with 1 1/2 litres of asparagus stock and simmer for about 5 minutes. Season to taste with salt, pepper, sugar and lemon juice. Stir egg yolk and 100 g whipped cream until smooth and add to the no longer boiling soup.
Cut cooked asparagus spears into pieces. Add to the soup. Whip 100 g whipping cream until half stiff. Sprinkle soup with whipped cream, chervil leaves and crushed pink berries.