Carry plate with potato-egg mixture and empty pan back to stove. Place the frying pan back on the range and put just enough oil to cover the bottom and sides of the pan - approximately 1 1/2 tsp. Let the pan warm for 30 seconds or so on medium to medium-low heat. Carefully slide the tortilla (which is probably still a bit runny), into the frying pan, using a spatula to catch any egg mixture that remains on plate or tries to run out. Use the spatula to shape the sides of the omelet. Let the omelet cook for 3-4 minutes. Turn the heat off and let the tortilla sit in the pan for 2 minutes. Carefully slide the omelet onto a large plate.