Clean and slice the mushrooms and finely dice the onion.
Heat up the pan and add the olive oil. Sauté the onions until fragrant and translucent, then add the mushrooms, salt, and pepper. Cook until the water that comes out from the mushrooms evaporates and the mushrooms begin to caramelize. Remove from the pan and set to the side.
For the ham and cheese filling:
Shred the cheese and cut the ham slices into small strips or squares.
For the omelette:
In a bowl, crack two eggs and whisk them well with a fork, using right to left movements until they becomes homogenous. The purpose of the movement is just combining the yolks and the whites, not incorporating air in the mixture.
Warm up the pan over medium low heat and add the butter. Once it melts, move the pan in a circular motion so the butter can cover it all over.
When the butter bubbles, add your eggs to the pan and let cook over medium low heat. Mix with a spatula slightly, just until the eggs begin to set. Bring all the irregular edges in and let the eggs set. Instead of being cooked until browned, French omelettes are cooked just until set, resulting in a creamy, custard-like texture and a light exterior.
Add a pinch of salt on top of the eggs as well as your filling of choice and fold the omelette in half or thirds.
Sprinkle some extra salt, fresh ground black pepper, and chopped chives over the omelette and serve with mustard and a small side salad.
Notes
Storage instructions
The French omelette is best served fresh but keeps well in an airtight container in the fridge for up to three days.
Additional Instructions
This recipe makes one omelette and has two filling options for you to choose from (the measurements are for one omelette). You can multiply the recipe by the amount of servings desired. It's best to cook one omelette at a time but you can prep multiple servings of the fillings together.
Nutritional Information Note
The nutritional information provided is an estimate for the omelette with the mushroom filling. Adding ham and cheese will increase the calories by approximately 100.