1. Add the diced potatoes to a large pot and cover with cold water. Bring to a boil, lower the heat and leave to simmer until cooked through (20-30 minutes). Drain, mash and season well with salt and pepper. Leave to cool while you make the filling.
2. Heat oil in a pan and sauté the onions with the beef for about 5-7 minutes. Add the garlic, mushrooms, chili flakes and season to taste with salt and pepper. Add beef stock and cook for about 8-10 minutes further. Take off the heat and fold in the chopped dill.
3. Mix the flour into the mashed potatoes. Take about 3 tablespoons of dough and flatten them out into flat patties. Add about a tablespoon of the mushroom beef mixture in the middle, then top with more of the potato mixture and shape into round potato cakes. repeat.
4. Heat some oil in a frying pan on high. Once the oil is hot, add the potato cakes and cook on each side for about 2 minutes or until golden brown. Serve with some extra dill and sour cream.