For the pike perch in a bed of vegetables, first dry the fish, sprinkle inside and out with lemon. Chop the onions and greens, sauté in butter except for the leek and cook for 15 minutes at low heat. Add the leek to the vegetables, season with salt and pepper and a pinch of sugar, pour in the wine and let it boil once.
Rub fish with sprinkling seasoning. Transfer vegetables and gravy to juice pan, add fish and cover with vegetables. Cover juice pan with aluminum foil and cook for 15 minutes at 200 degrees. Keep the covered fish warm.
In a saucepan, bring vegetables and gravy to a boil once with crème fraîche and instant sauce, stirring. Add finely chopped kitchen herbs. Pour sauce over the fish with the vegetables. Serve the pike perch in a bed of vegetables.