Preheat the oven to 190°C. Peel potatoes, boil, mash with 100 ml of milk.
Cut the fish into pieces 3×4 cm, boil in 500 ml of water and 100 ml of wine for 5 minutes. Drain the broth, put the fish in a baking dish. Peel shrimp, chop coarsely and mix with pieces of fish.
Chop the onion and fry in butter. Add eggs, cream, salt, pepper, thyme. Mix until a homogeneous mass is obtained. Pour in the fish. Put the finished puree on the fish, crush on top with a spoon. Place thin slices of butter on top.
Bake for 30-35 minutes. Decorate with greenery.