In a large non-stick skillet, heat the olive oil over medium heat.

Add the sliced mushrooms and sauté until softened, about 4-5 minutes.

Add the fresh spinach to the skillet and sauté until wilted, about 2-3 minutes.

Remove the mushrooms and spinach from the skillet and set aside.

In a bowl, beat the eggs and season with salt and pepper.

Pour the beaten eggs into the skillet and cook until the edges start to set.

Gently lift the edges of the omelette and tilt the skillet to allow the uncooked eggs to flow to the edges.

Once the eggs are mostly set, spoon the sautéed mushrooms and spinach onto one side of the omelette.

Sprinkle the shredded cheddar cheese over the mushrooms and spinach.

Fold the other side of the omelette over the filling and cook for another minute, or until the cheese is melted.

Slide the omelette onto a plate and serve hot.