Wash the fish, dab dry and cut through once lengthwise. Sprinkle with lemon juice and season with salt and pepper. Wash parsley, chives and dill and dab dry. Chop parsley and dill finely, cut chives into small rolls.
Mix the herbs. Spread half of the herbs on the plaice fillets, roll them up and pin them with a wooden skewer each. Place the plaice rolls in a lightly greased casserole dish. For the sauce, bring cream and wine to the boil in a saucepan.
Add mustard and remaining herbs and stir in. Add sauce thickener while stirring and bring to the boil again. Season to taste with salt and pepper. Pour sauce over the plaice rolls and sprinkle with crabs.
Cook in the preheated oven (electric cooker: 200 °C/ gas: level 3) for 15-20 minutes. Serve garnished as desired with lemon wedges, parsley and dill. Boiled potatoes taste good with it.