Peel and roughly grate the jacket potatoes and mix loosely with salt. Cut the smoked bacon into fine cubes. Heat the diced bacon and butter in a pan. Add the grated potatoes and fry lightly on all sides, turning them frequently. Then push them together to form a cake, press firmly to the bottom and put the lid on the pan. Fry for 20 minutes on a low heat. Then sprinkle 2 tablespoons of milk over it and fry for another 10 minutes. Then serve.
Rösti are prepared in the various Swiss cantons with minor changes. The Zurich variant leaves out the bacon and another preparation is that with raw potatoes.