Heat a large skillet over medium heat and add the 1 teaspoon olive oil.

Add the minced garlic and cook, stirring, about 30 seconds until fragrant (do not let it brown).

Add the sliced mushrooms and sauté, stirring occasionally, about 10 minutes, until softened and lightly browned.

Stir in the minced parsley, turn off the heat, transfer the mushroom mixture to a bowl, and set aside. Leave the skillet on the stove (do not wash) so the remaining oil stays in the pan.

Separate the 3 large eggs, placing the yolks in one bowl and the whites in another.

Whisk the egg yolks until thick and slightly pale.

Beat the egg whites until white and frothy and soft peaks begin to form (you may use a blender or electric mixer if you prefer).

Gently fold the beaten whites into the yolks in two additions, being careful not to deflate them.

Fold the 1/4 cup shredded cheddar cheese into the combined egg mixture.

Return the same skillet to low–medium heat and warm it for about 30 seconds.

Pour the egg mixture into the skillet, spread it evenly, cover with a lid, and cook until the bottom is set and the top is mostly set (about 3–5 minutes), checking occasionally.

Use a spatula to loosen the edges and under the omelette, then spoon the reserved mushroom mixture onto one half of the omelette.

Carefully fold the other half over the mushrooms, cook 30–60 seconds more to melt the cheese, then slide the omelette onto a plate and serve hot.