Peel your spuds and cut them into thin matchsticks using a mandolin or coarse grater. Mix them with some rock salt and set aside for about 10 minutes to allow the salt to draw out water from the potato.
Wrap the potato matchsticks in a clean tea towel and squeeze to get rid of as much liquid as possible. Toss them through with a little oil or clarified butter and season with pepper.

Heat some oil in a hot frying pan. Sprinkle a thin layer of the potato into the pan and dot over a few knobs of butter. Cook until the potato on top starts to turn translucent and the bottom is golden and crisp, then flip the rosti over to brown the other side - potato perfection!