Boil potatoes (5 PCs.) in a uniform until half-cooked. Cut into rings with a thickness of approximately 0.7 - 1 cm.
Add salt and pepper to taste on both sides of the halibut fillet without skin and bones.
In a bowl, add sour cream (4 tablespoons), add mustard, add dried rosemary (1/2 teaspoon), add salt and ground white pepper, add 3 tablespoons of water. Stir the mixture.
Chop the carrots into rings/straws /curly plates. Add 3-4 tablespoons of vegetable oil to the bottom of the baking dish, then put the potatoes, add a layer of potatoes with a little salt, then put the chopped carrots.
Chop the shallots into rings. Put onion rings on the carrot layer.
RUB the halibut fillet liberally with mustard and sour cream sauce. Add the halibut fillet to the baking dish. Once again, sprinkle the structure with vegetable oil. Cover the form with a sheet of foil and send it to the oven preheated to t190c. Bake for about 20-25 minutes. 5-10 minutes before cooking, remove the foil and brown the top layer of fish on the grill.