In a small bowl, lightly beat together the eggs, just until the yolks and whites have combined.
Heat a nonstick skillet (I used half of a frittata pan) over high heat and melt the butter, moving the pan around to distribute it evenly. When the butter begins frothing lightly, pour in the egg mixture.
Give the eggs 2 to 3 seconds to form a slight surface on the bottom. Then, begin shaking the pan towards you, holding it at a slight angle. Add asparagus and mozzarella.
As the mixture solidifies, continue moving the pan back and forth. Then increase the angle slightly to encourage the omelette to fold over onto itself. If it doesn’t naturally, you can use a fork to help it along.
Let the omelette cook a bit longer until it reaches your level of desired doneness, and slide it onto your plate.