Start it the night before.

8 center-cut bacon slices $ 1 1/2 cups chopped onion $ 8 ounces sliced shiitake mushroom caps 3 garlic cloves, minced 2 cups shredded hash brown potatoes (such as Simply Potatoes) 1/4 cup no-salt-added chicken stock (such as Swanson) 5 cups fresh baby spinach $ 2 tablespoons thinly sliced fresh basil 1/2 teaspoon kosher salt, divided 1/2 teaspoon freshly ground black pepper, divided 3 ounces reduced-fat Swiss cheese, finely chopped $ Cooking spray $ 1/2 cup 1% low-fat milk $ 6 large eggs, lightly beaten

1. Cook bacon in a large nonstick skillet over medium heat until crisp. Remove bacon from pan; crumble. Increase heat to medium-high. Add onion, mushrooms, and garlic to drippings in pan; sauté for 6 minutes. Add potatoes and stock; cook 6 minutes, stirring frequently. Add spinach, basil, 1/4 teaspoon salt, and 1/4 teaspoon pepper; cook 2 minutes or until spinach wilts. Remove from heat; let stand 10 minutes. Stir in crumbled bacon and cheese. Place mushroom mixture in an 11 x 7-inch broiler-safe glass or ceramic baking dish coated with cooking spray. Cover and refrigerate overnight.
2. Preheat oven to 350°.
3. Uncover dish. Combine remaining 1/4 teaspoon salt, 1/4 teaspoon pepper, milk, and eggs in a medium bowl. Pour egg mixture over mushroom mixture. Bake at 350° for 28 minutes.
4. Preheat broiler to high; remove dish while broiler preheats. Broil 3 minutes or until top is browned and just set. Let stand 5 minutes.