Preheat the oven to 350 degrees. In a large ovenproof skillet over medium high heat, add the olive oil and sliced onion. Cook for 10 minutes, stirring occasionally. White the onion is cooking, whisk the eggs, milk, salt, pepper, and half of the parmesan in a large bowl.
After 10 minutes, add the minced garlic to the onions and stir for 1 minute. Add the egg mixture to the hot pan. Next, carefully layer the zucchini and asparagus on top of the frittata in a pretty design.
Season the top with a pinch of salt and pepper. Place the mozzarella balls evenly in the frittata and sprinkle with the rest of the parmesan. *This frittata is very versatile. If you prefer different cheeses or vegetables feel free to experiment. If you want your vegetables to be more “well done” then “aldente” feel free to roast or steam the vegetables ahead of time before placing them into the frittata. If you have any leftover cooked vegetables this would be a great place to use them*
Bake for 15-18 minutes until the eggs are cooking through. Garnish with fresh basil. Serve with a salad such as strawberry spinach salad.