In a small skillet, heat 1 tbsp of olive oil over medium-high heat.

Add the sliced portobello mushroom and saute until golden brown. Set aside on a plate.

In a small bowl, add the eggs, parsley, salt, and pepper. Beat until well combined.

In the same skillet, spread the remaining olive oil to coat the bottom and sides evenly, and heat over medium heat.

Pour the egg mixture into the skillet and let sit for a minute.

On one half of the egg, add the grated Swiss cheese followed by the sauteed portobello mushroom.

Cook until the bottom starts to set and a skin forms.

Using a rubber spatula, lift the edges of the omelette, folding the untopped side over the other.

Let cook for a minute longer before sliding the omelette onto a plate.