Peel the turnips and cut each into four pieces. Put in a pot, add 2-3 tablespoons of water, close the lid tightly. Steam in the oven at 150 C for 1-1.5 hours.
Drain the water, add a little butter, salt, pepper to the finished turnip and mix (if desired, you can steam the turnip).
Clean the zander, remove the entrails and fins. Cut the fish into 6 portions, save the head. Peel the onion and cut into 8 pieces.
Place the pieces of fish and the head in a single layer in the form, spread the onion between them, add peppercorns and pour milk so that the fish is almost covered.
Bring to a boil over low heat, cook for 10-15 minutes. Remove the onion and fish head, salt and pepper the fish and broth, put pieces of butter on the fish.
Place the mold in an oven preheated to 150C for 10 minutes. Remove, cover and leave for 20-30 minutes. Serve fish with milk broth and steamed turnips.