The potatoes for Rosti should be baked one day ahead and refrigerated. Slice thinly or grate them and press into the pan so that they "stick" together. You can put a weight on them if you want to. Sprinkle lightly with milk or cream. Make sure the pan lid is tight fitting and DON'T TOUCH the potatoes. If you disturb them or attempt to stir them around you will wind up with, yep, stir fried potatoes. Rosti should form a nice brown crust on the bottom. Take them out of the pan in one piece if possible by inverting the pan and dishing them brown side up. If you do all of these things you will have a perfect round, pressed Rosti dish.