Add minced garlic and spinach leaves and cook for another 1-2 minutes, just until garlic is fragrant and spinach leaves are soft but not wilted.
Remove from heat and add the mushroom and spinach mixture to the bowl with your whisked eggs. Season with salt and pepper.
Add mixture back to oven safe pan and top with parmesan cheese.
Place the frittata in the center rack in the oven and bake until eggs are just set, about 10 minutes.
Once finished, move pan to top rack and broil for 2 minutes to lightly brown the cheese on top.Remove from oven and allow to cool slightly before serving.
Optional Garnish - Roasted Cherry Tomatoes
Place tomatoes lightly drizzled with olive oil on a sheet pan in 350 degree oven for about 5-7 minutes. Remove from oven and place on top of frittata