Brussels Sprouts and Butternut Squash Frittata

Ok, I get it that it's officially spring but as I made this one a couple days please humor me with one more squash recipe. This will serve four or make for some tasty leftovers the following day:)

Ingredients:
5 large whole eggs
1/2 cup egg whites
1/2 tsp sea salt, divided
1/8 tsp tsp fresh ground black pepper
1 1/2 tsp olive oil
4 oz Brussels sprouts, trimmed and quartered
2 1/2 oz white button mushrooms, thinly sliced
1 cup peeled and diced butternut squash (1/4 inch cubes)
1 large shallot, minced
1 spring fresh rosemary,  leaves minced
1 large clove garlic, minced
1 oz goat cheese, crumbled
2 tbsp grated Parmesan cheese

Directions:
Preheat oven to 375 degrees F.
In a medium bowl, whisk eggs, egg whites, 1/4 tsp salt and pepper, set aside.
In a 10 inch nonstick ovenproof skillet, heat oil on medium. Add Brussels sprouts, mushrooms, squash, shallot, rosemary and remaining 1/4 tsp salt. Saute, stirring often, until mushrooms and squash are tender and Brussels sprouts are almost cooked through, about 4 minutes. Add garlic and sauté for 1 more minute. Arrange vegetables in an even layer in skillet.
Pour egg mixture over top and gently shake pan to distribute evenly. Sprinkle with goat cheese and Parmesan and cook undisturbed until edges set, about 3 minutes. Transfer to oven and cook until eggs are completely cooked through and cheese melts, 10 to 12 minutes. To serve, carefully invert into a plate.