Peel and wash the carrots, onions, garlic, and champignons. Clean the chicken thighs, wash and dry. Cook the buckwheat until half cooked.
Separate the chicken meat from the bone and cut into small pieces, add mustard and ground pepper. Place in a baking dish.
Chop the onion, grate the carrots, fry in a frying pan, place everything on top of the meat.
Chop the mushrooms, fry, mix with buckwheat and add salt. Then spoon everything over the vegetables.
Make a fill. To do this, mix eggs, sour cream, garlic. Pour this mixture over the buckwheat and place in the oven for 30 minutes. Then grate the cheese and sprinkle it over the casserole. Place in the oven for another 10 minutes and bake at 180 degrees.
Serve the casserole in neat portions. Place a sprig of parsley and a teaspoon of grainy mustard nearby. Slice the tomato and place it on the side near the casserole. Apply a pattern on top with any sauce to your taste.