Whisk two eggs, set aside.
Warm omelette pan on medium-high heat.
Add 1/2 Tbsp olive oil and warm, but not to the point of smoking.
Add garlic and sauté slightly.
Add mushrooms, tomatoes, olives, spinach and basil. Sauté together until spinach is wilted and mushrooms are cooked.
Remove ingredients from pan and transfer to a separate dish.
In same pan, warm remaining 1/2 Tbsp olive oil until warm.
Add eggs to pan and cook as you would a normal omelette. See my daughter's tutorial in this post if omelette making is new to you.
Add all cooked ingredients to the inside of the omelette.
Sprinkle some of the feta inside and some of it on top.