Peel the potatoes and cook 10 minutes in salted water, then carefully hollow without very thin walls. Onions and mushrooms are cleaned, cut into small pieces and sauté in half of the oil until soft. Stir in the tomato puree and season with salt and pepper. Potatoes filled with the prepared stuffing and arrange in a baking dish. Around put hollowed part of the potatoes, cut into pieces and mixed with the remaining stuffing (if any). Serve sprinkled with salt and pour the remaining sunflower oil and 1 cup hot water. Bake 25-30 minutes in a moderate oven. When serving on each potato is placed in one olive.