Wash the carp without damaging the outer skin. Season inside with salt and pepper. Bring 1/4 liter vinegar to the boil. Place an inverted cup in the carp belly so that the carp can be set up.
Place the carp carefully on the fat pan of the oven. Pour vinegar evenly over the carp until it is blue. Add 1 litre of boiling salted water. Cook in the preheated oven (electric cooker: 150 °C/ circulating air: 125 °C/ gas: level 1) for 40-50 minutes.
Peel, wash and halve the potatoes and cook in boiling salted water for about 20 minutes. For the sauce, melt 2 tablespoons of butter in a saucepan. Stir in flour and sweat briefly. Add vegetable stock and milk while stirring.
Bring to the boil, cook for 3-5 minutes and stir in horseradish. Season to taste with salt and pepper. For the vinaigrette, whisk 4 tablespoons of vinegar, salt, pepper and honey. Add the oil drop by drop.
Peel the shallot, cut into fine cubes and stir into the vinaigrette. Clean and wash the salad, spin dry and pluck into bite-sized pieces. Wash parsley, shake dry, pluck leaves from the stalks and chop.
Melt 2 tablespoons of butter. Fry the potatoes and parsley in the butter. Arrange potatoes and carp on a plate. Garnish with orange and dill. Add salad.