Divide the cleanly parred pike-perch into portions and score the skin side a few times without cutting into the fish flesh.
Drain the sauerkraut prepared according to the basic recipe in a sieve, mix with the grapes and keep warm.
For the sauce, boil the sauerkraut stock, add the fish stock, reduce to a slightly syrupy consistency, add the cream, mix briefly and add butter.
Season the pike-perch, turn it in flour on the other side, roast it in clarified butter first on the skin side and then on the other side until golden brown, arrange it on sauerkraut and pour the sauce around it.
This is best served with boiled potatoes.