Peel, grate and squeeze the potatoes. Peel the onions and cut into cubes.
Put the eggs with the crème fraîche, salt, pepper and the onions in a bowl and mix with a mixer, then mix with the potatoes and breadcrumbs and place in a sieve.
Heat oil in a pan and fry the buffers until golden brown on both sides. Place the potato mixture in a sieve in portions while frying so that the potato water can drain off.