Preheat the oven to 200 ° C fan-assisted air. Wash the potatoes well, prick on all sides, place on pieces of aluminum foil and season with salt and pepper. Brush with oil, close the aluminum foil packet and bake in the preheated oven for 50 to 60 minutes.
In the meantime, put the quark in a bowl. Pour half of the dill over it. Season with salt and pepper. Add the rosemary powder and stir well.
Put the sour cream in a bowl. Squeeze in the garlic or chop it finely and add. Add the cream cheese, tartar sauce and the remaining dill. Season with salt and pepper and stir well.
Put the egg in a deep plate and whisk with a fork. Put the breadcrumbs in another deep plate. Season the plaice fillets with salt and pepper and turn them individually, first in the egg and then several times in the breadcrumbs. Fry the breaded plaice fillets about 15 minutes before the potatoes are ready in a pan over medium heat and in plenty of oil until they are golden brown.