Preheat the oven to 375°F (190°C).
Heat olive oil in a skillet over medium heat. Add onions and sauté until soft.
Add mushrooms and cook for 5 minutes until tender and browned. Add asparagus and cook for another 3 minutes.
In a bowl, whisk eggs with salt, pepper, and herbs. Pour the egg mixture over the vegetables in the skillet.
Sprinkle grated cheese on top, if using.
Transfer the skillet to the oven and bake for 10 minutes, or until the eggs are set and lightly browned.
Let the frittata cool for 5 minutes before slicing and serving.