Boil the peeled potatoes until soft, then mash them in a bowl until smooth.

Finely chop mushrooms and onion. In a skillet, heat sunflower oil and sauté the onion until golden, then add mushrooms and cook until tender.

Add the sautéed vegetables to the mashed potatoes. Stir in the egg and flour to bind the mixture.

Shape the potato mixture into patties and fry them in a skillet with sunflower oil until golden brown on both sides, about 3-4 minutes each.

Serve warm with sour cream on the side. Leftovers can be stored in the fridge and reheated in a skillet for added crispiness.