Preheat oven to 350 degrees.
In 8 inch cast iron skillet, or other oven-proof skillet, heat olive oil over medium high heat.
Add leeks to skillet and saute for 5 minutes.
Add asparagus, mushrooms and fresh thyme to pan. Saute 5 minutes
Sprinkle vegetables with salt and pepper. Stir.
Crack 8 eggs into medium size bowl. Using a fork, lightly beat until combined.
Turn heat in skillet down to low. Add beaten eggs and 1/2 cup of parmesan cheese. Cook for a couple of minutes until bottom is set.
Place skillet in 350 degree oven and cook for 8 minutes.
Top Frittata with remaining 1/2 cup cheese and put under broiler until cheese melts.
Remove from oven. Let sit for a couple of minutes. Cut into wedges and then serve.