Breakfast Strata with Sausage, Spinach, and Leeks

Spray a 13x9-inch baking dish with cooking spray.

In a large skillet, melt 3 tablespoons butter over medium-high heat. Add leeks and garlic; cook, stirring frequently, until softened, about 5 minutes. Remove leeks, and add sausage. Cook over medium heat until browned, 6 to 8 minutes; remove sausage and let drain.

In same skillet, melt remaining 2 tablespoons butter over medium-high heat. Add mushrooms and 1 teaspoon salt. Cook, stirring occasionally, until mushrooms are browned and tender, about 10 minutes. Stir in spinach; cook until wilted.

In a large bowl, whisk together eggs, cream, milk, mustard, pepper, and remaining 1 teaspoon salt. In another large bowl, place cubed bread. Pour egg mixture over bread. Add leeks, garlic, sausage, mushrooms, and spinach; toss to combine. Pour mixture into prepared pan. Cover and refrigerate overnight.

Remove from refrigerator, and let stand for 30 minutes.

Preheat oven to 350°.

Bake until golden brown and a wooden pick inserted in center comes out clean, 45 to 50 minutes.