Cut the ready-to-cook carp into pieces 3 to 4 cm wide.
Bring the water with the fish seasoning to a boil, then add the fish pieces so that they are barely covered with water. Cook on low to medium heat for about 7 minutes.
In the meantime, let the sugar turn brown in a saucepan, deglaze with malt beer, dust in the flour, stir and season with salt and vinegar. Pour the butter in flakes into the sauce, fold in, then lift the carp pieces out of the water, drain briefly and add to the sauce. Let it steep again and serve hot with boiled potatoes.