Scrub the potatoes, wash them thoroughly, cut them in half and cook them in little boiling salted water for about 20 minutes. In the meantime, wash and grate cucumbers and season with salt. Leave to stand for a while, squeeze and fold into the quark.
Peel and chop the onions. Wash tarragon and chop finely, except for something to garnish. Add onions and tarragon to the quark and mix everything. Season with salt and pepper. Arrange potatoes and quark on plates.
Sprinkle with prawns, grated lemon peel and sea salt. Garnish with tarragon.