Wash the asparagus, cut off the woody ends. Cut the bottom half of the asparagus into slices. Cut the upper part into pieces. Peel and chop onion and potato. Heat 1 tablespoon of oil in a saucepan.
Sweat onion, asparagus pieces and potatoes in it, then deglaze with broth. Season soup with salt and pepper and simmer for about 10 minutes. Add cream and let it simmer again for about 10 minutes.
Meanwhile wash the herbs and put 3 stems of chervil aside. Pluck off the remaining leaves and chop them finely. Put the slices of bacon in a pan without fat and let them drip off on kitchen paper. Toss the asparagus slices in the fat for 2-3 minutes, then add the crabs.
Puree the soup and season to taste with salt, pepper and possibly some lemon juice. Add the herbs. Fill the soup into plates, then add the crabs, asparagus and bacon to the soup. Garnish with chervil.