Preheat oven to 425 degrees F.
In medium bowl, whisk eggs, milk, salt and pepper together well. Add 1/2 cup cheese. Set aside.
In cast-iron skillet, cook bacon until crisp. Let drain and cool on paper towels; crumble. Drain all but a tablespoon or so of drippings from skillet and cook garlic and onion a few minutes until soft and translucent.
While bacon is cooking, steam asparagus until tender (several minutes). Put in skillet with garlic and onion. Add spinach and cook until just wilted. Arrange ingredients in skillet evenly.
Add crumbled bacon to the egg mixture, give it another whisk and then pour over the vegetables in skillet. Without stirring, cook over medium heat for about 5 minutes or until eggs begin to set. Sprinkle remaining cheese over top.
Bake 10-15 minutes, until middle is barely set.