Peel potatoes and grate into a bowl. Using a hand grater with large holes is the traditional way
Melt 2-4 Tbsp. butter in an 8-inch non-stick pan. Add the grated potatoes about 1 inch deep and add salt to taste.
Cook over medium heat for 3 or 4 minutes, stirring occasionally to coat the potatoes evenly with butter. Pat the potatoes into a cake with a spatula and let cook for 10 minutes, uncovered. Cover and cook for another 5 to 10 minutes.
When the bottom of the potato cake is golden brown, place a plate, just slightly smaller than the pan, inverted over the potatoes. Then invert the pan, holding onto the plate. Remove the pan and set it back on the stove. Add another tablespoon of butter and let it melt.
Slide the Rosti back into the pan, golden side up, and cook about 15 minutes longer, pressing down once or twice to make the pancake stick together more. You can cover it to get the potatoes cooked in the middle, but remove the cover at least 5 minutes before the end so that your pancake is crispy on the outside.
Slide the Rosti onto plate and serve by cutting into wedges. Salt and pepper to taste.
NOTE: You may also add parsley, onions, nutmeg or ground paprika.