Cut the fins off the perch carcass. The perch's fins are very sharp, so it's easier to cut them off with scissors so you don't get hurt. Use a knife to remove the scales. The scales are easier to separate from the skin if you pour boiling water over the fish. Remove entrails and bones. Rinse the carcass with water. Cut the leek into thin rings.
Prepare the pan for the oven. Cover it with parchment paper so that there is a free edge on all sides. Place leek rings on paper. Place the perch fillet on top. Salt and pepper the top of the fish.
Crush the garlic clove in a press and add to the cream. Stir. Gently pour the cream and garlic mixture over the fish.
Wrap the parchment on all sides like an “envelope.” Preheat the oven to 200 degrees and place the pan with the perch there. Bake for 30 minutes.
Juicy and soft sea bass is ready. Transfer the fish along with the onions to a plate. Sprinkle finely chopped green onions on top.
To serve, use containers of contrasting color.