I think the most important thing is getting the right potatoes, "festkochend", so the ones you use for roast potatoes not the ones you use for mash. I then work on 2 med potatoes per person +-. Boil them for about 5 mins in their skins. Let them cool (the Swiss leave them overnight I believe) & pull of the peels. Grate coarsely. Melt about a teaspoon of butter in a good pan, add a bit of oil so the bottom is covered. When the pan is hot add some of the potatoes, to cover the bottom and be about 1/2cm deep or just work out how many people you are feeding at 1/2 roesti per person. Let if fry a bit on medium. Press the potatoes down with an egglifter every now and then and slide your egglifter along the edges. Lift the potatoes now and then to check the bottom. Once it's solid (but not sticking to the pan which happens when the pan is too hot) put a dinner plate upside down on the pan, invert it quickly so the cooked side is on top, and slide back into the pan. Cook a bit longer, pressing down into the pan and sliding the spatula along the edges as before, check the underside and when cooked slide off into a plate. I normally have 2 pans going at the same time to speed things up. En guete!