Mediterranean Spinach Strata Recipe

Ingredients

• 2 (8 ounce) loaves French bread baguette, cut into 1-inch-thick slices
• Cooking spray
• 1 cup chopped onion
• 4 garlic cloves, minced
• 1 (8 ounce) package presliced mushrooms
• 1 tablespoon all-purpose flour
• 2 (7 ounce) bags baby spinach
• 1/2 teaspoon salt, divided
• 1/2 teaspoon black pepper, divided
• 3 cups thinly sliced plum tomato (about 1 pound)
• 1 (4 ounce) package crumbled feta cheese
• 3/4 cup (3 ounces) grated Asiago cheese, divided
• 3 cups fat-free milk
• 2 tablespoons Dijon mustard
• 1 1/2 teaspoons dried oregano
• 5 large eggs, lightly beaten
• 4 large egg whites, lightly beaten