Two kinds of fish on sauerkraut cooked in wine with horseradish and beurre blanc sauce

Ingredients: 

200 g of sea bass
200 g of red mullet
250 g of sauerkraut (ideally from the weekly market, freshly mashed)
1 shallot 
500 ml of dry white wine (for example Franken Riesling)
250 g of cold butter (in slices)
20 g of white pepper corns
bay leaf
juniper berries
2 tablespoons of crème fraîche
Sea salt, pepper, sugar
50 g of LieblingsKren
1 small onion
fresh dill for garnishing
2 tablespoons of oil

Preparation for beurre blanc sauce: 

Reduce 200 ml of wine, chopped shallots, LieblingsKren and peppercorns to a half. Then stir in the crème fraîche, simmer gently for 5 minutes, strain and put to the side. 

Preparation for sauerkraut cooked in wine: 

Soak sauerkraut well (1 day beforehand), cut onion into fine strips and sweat in oil until translucent, add sauerkraut and cover with 250 ml of white wine, add juniper berries and bay leaf and boil for around 1 hour, season with salt, sugar and pepper. 

Preparation for fish: 

Cut the fish filets into 4 equal pieces of 50 g each, place in a buttered pan and cover with a little white wine. Poach for around 2-3 minutes with the lid on. Then add 3 tablespoons of the fish stock to the beurre blanc sauce. Bring the beurre blanc sauce to a boil again and stir in the cold butter with a whisk, do not let it come to a boil any more as otherwise the sauce will curdle. 

Serving suggestion: 

Place the sauerkraut cooked in wine in the middle of the plate, put the poached fish filets on top and pour on the horseradish and beurre blanc sauce. Garnish with fresh dill.