Boil the potatoes in salted water until just tender (about 15 minutes). Drain and cool completely — best if left overnight in the fridge.
Slice the cold potatoes into 0.5 cm slices.
Heat butter or bacon fat in a heavy frying pan (cast iron works best).
Add the potato slices in a single layer. Let them fry undisturbed for a few minutes before turning.
Once golden, add onions and bacon. Continue frying until everything is crisp and aromatic.
Season with salt, pepper, and fresh herbs before serving.
Serve hot with bratwurst, frankfurters, or a fried egg — and you’ll have one of Germany’s most comforting meals.