Peel, wash and slice the potatoes. Put potato slices in boiling salted water and cook for about 5 minutes. Pour potatoes onto a sieve and drain. Wash the plaice fillets, dab dry and halve lengthwise.
Sprinkle the fillets with lemon juice and salt. Peel and finely dice the shallot. Wash tarragon, chives and parsley and dab dry. Chop tarragon finely, except for a little bit for garnishing.
Mix half of the tarragon and the shallots cubes. Chop the parsley and cut the chives into small rolls. Mix with remaining tarragon and shallots. Spread the herb mixture on the plaice fillets, roll them up and pin them with wooden skewers.
Place the potatoes and plaice rolls in a greased, ovenproof dish. Sprinkle the remaining shallots and tarragon mixture over the potatoes. Pour cream sauce over them and sprinkle with shrimps. Bake in the preheated oven (electric cooker: 225 ° C/ gas: level 4) for about 15 minutes.
Serve garnished with remaining tarragon.