Crack the eggs into a mixing bowl with a pinch of salt and pepper.

Whisk the eggs with a fork until smooth and frothy. Add salt and spices to taste. Melt butter in a frying pan.

Once the butter has melted, pour in the egg mixture. When the omelet begins to cook and get firm, but still has a little raw egg on top, sprinkle cheese, mushrooms and onion on top (optional). Using a spatula, carefully ease around the edges of the omelet, and then fold it over in half.

When it starts to turn golden brown underneath, remove the pan from the heat and slide the omelet on to a plate.