When the potatoes and onions are done, make an omelette with your mixture. You need to add a little fat to a flat or omelette pan. Heat the fat, gently pour in the egg mixture. Keep running a fork through the omelette making sure it stays together as one, but becomes fluffy. Do this until the top is just shiny. The egg will carry on cooking. Remove with the cooked side down from pan onto a serving plate. Add the potato and onion mix on half of the omelette