Divide the pike-perch fillet into portion pieces, season them with salt, pepper and juice of one lemon. Lightly flour. Fry in hot oil and half of the butter until golden brown. In the rest of the butter, sauté the beets and parsley roots cut into sticks, extinguish with tarragon vinegar and simmer gently for 10 min (should still be crunchy). If necessary, add a little more white wine. Season with salt and pepper. Add the coarsely chopped parsley.
Arrange the vegetables on warm plates, evenly distribute the fish fillets on top and pour a little of the sauce.
For the sauce, reduce the white wine, fish stock and shallots to about an eighth of a liter of liquid. Add the whipping cream, cook a little more, season with salt and pepper. Blend with a hand blender, stir in horseradish and the whipped cream before serving.
Tip: Instead of beet use fennel cut into strips.