Wash the potatoes. Cook in boiling water for about 20 minutes. Meanwhile peel the asparagus, cut off the woody ends briefly. Season salt water with lemon slice and sugar, bring to the boil.
Cook the asparagus for about 15 minutes at medium heat. In the meantime, wash and chop the chives for the dip. Peel and finely chop the onion. Mix yoghurt, chives and onion. Season with salt, pepper and lemon juice.
Mix in the prawns, stir slightly thinner with 2-4 tbsp. asparagus stock, season again. Drain potato water. Place briefly with closed lid on the hot stove. Arrange the asparagus on a plate and pour the sauce over it.
Add the potatoes.