Cook potatoes, in their jackets, in boiling water until about half cooked, 15 minutes. When cool enough to handle, slip off skins. Shred potatoes coarsely into a mixing bowl. Mix lightly with onions, salt, and white pepper. Shape into 8 patties. In a skillet, heat oil over low heat. Add patties. Cook over low heat, without stirring until potatoes are brown and crusty on bottom, 15 minutes. Loosen edges with a spatula and flip carefully over and cook for 15 minutes more or until brown and crusty. Repeat with remaining patties.