Peel the asparagus and cut off the woody ends. Boil up plenty of water with salt, pepper, sugar and lemon juice. Cook the asparagus in it at medium heat for about 20 minutes. In the meantime, remove the crayfish from their skins, except for the tail. Remove intestines. For the vinaigrette, wash the chives and cut into fine rolls.
Mix egg yolk, vinegar, chives, mustard and 3 tablespoons of asparagus stock. Season with salt and pepper. Gradually add the oil and season to taste again. Mix asparagus and vinaigrette and let it steep a little. Arrange the asparagus and crayfish with the vinaigrette on plates. Serve garnished with a little rocket, dill and lemon slices