Rinse and dry the perch fillets.
Sauté the onions until golden, extinguish with the white wine and add the fish stock. Cook by at least half until the sauce is thickened.
Rinse and dry the sorrel leaves and cut them into strips.
Season the sauce with salt and freshly ground pepper to taste, add half of the sorrel strips and gently! warm up the sauce.
Roast the perch fillets in the stem pan in 4-5 min until golden brown.
Salt, season with pepper and drizzle with juice of one lemon.
Serve the fried fillets together with the sorrel sauce. Evenly distribute the remaining sorrel strips on the fillets.