a bowl. mix in the cooled potato/onion mixture.
heat a non-stick pan (the best option, trust me!) over medium-high heat, add a little oil if you want (i do) and pour mixture into pan. give it a shake to evenly distribute the egg mixture.
cook until the bottom begins to brown and the top begins to set.
now the tricky part. take a plate or pot lid which is larger than the pan, remove the pan from the heat, and cover the pan with the plate/lid. try to get a plate/lid which is fairly flat.
holding the plate/lid in place with one hand, flip the pan over so the tortilla is now bottom side 