Wash the potatoes and boil in boiling water for 20-25 minutes. Drain the potatoes, rinse and cool slightly. In the meantime peel and finely dice the onions. Peel and slice the potatoes.
Heat clarified butter in a large frying pan. Fry the potatoes for about 10 minutes while turning them over. Add the diced onion about 2 minutes before the end of the cooking time. Season with salt and pepper.