Cut mushrooms and leek. Grind parmesan and set aside.
Oil and heat a frying pan. Stir-fry mushrooms and leek until cooked. Season with salt and pepper. Set aside. Add oil and make omelette in the same pan.
In a bowl beat eggs until combined. Add salt and pepper. Pour into the pan.
Gently push cooked portions from edges toward the center so that uncooked eggs can reach the hot pan surface. Continue when no liquid eggs remain.
Add mushrooms on top and sprinkle with Parmesan. Fold the omelette in half. Serve.