Pre heat your grill to full.
In a medium sized frying pan approx. 24cm or 9½ inches, heat the butter and olive oil.
If you are using raw ingredients such as bacon or mushrooms fry them until cooked.
Beat the eggs in a bowl and season with salt and pepper.
Pour into the frying pan covering your fillings.
As the egg starts to cook, using a spatula, pull the edges into the centre allowing the raw egg to run outwards. You don't want the egg to be completely cooked in the middle.
Take the frying pan off the heat and sprinkle with the grated cheese if using.
Place under the hot grill. The omelette will puff up, the cheese will melt and it is done when it is starting to brown.
Fold over (optional) and serve on a plate.