Spinach Mushroom Strata Recipe

Ingredients

• 5 ounces frozen spinach, thawed
• 2 tablespoons unsalted butter
• 1 cup finely chopped onion (1 medium)
• 5 ounces chopped mushrooms
• 1 teaspoon salt (divided)
• 1/2 teaspoon black pepper
• 1/4 teaspoon freshly grated nutmeg
• 4 cups whole wheat bread, cubed (1 inch)
• 3 ounces coarsely grated gruyere (1 cup)
• 1 ounce finely grated parmesan cheese (1/2 cup)
• 1 1/2 cups milk
• 4 large eggs
• 1 tablespoon Dijon mustard