Shred onion and sautee in oil. Add tomato cubes, chopped spring onion and stew for 5 minutes. Put shredded sorrel and spinach leaves, chopped garlic, cook through, season with chopped greens and stir up.

Divide fish into fillet, cover with prepared mixture, make rolls, arrange in stewing pan, add salt, pepper, pour with water at half and simmer until done for 1 hour.

Serve the fish with the sauce from stewing, topping with lemon slices.