I use a small non stick pan to cook it with.

For this omelette shown, here are the ingredients:
2 Eggs beaten
2 Egg whites beaten
6 Baby plum tomatoes
2 mushrooms
Handful of spinach
Grated cheese (the size of about 3 lego bricks)
Pinch of salt
Black Pepper

 

Feel free to add what ever ingredents you like.

Method
Cut the tomatoes and mushrooms and fry in the pan until almost cooked.
Add the spinach. I like to chop my spinach first.
Once they are all cooked and the spinach has wilted, add the eggs, egg whites and grated cheese and seasoning.
Turn on your grill
Turn the heat of the pan down and cook for about 5 minutes and you will see the edge of the omelette becoming firm.
Transfer to the grill and cook until golden brown.
Transfer on to a plate and enjoy!