Cinc: Spinach, Mushroom, and Cheese Strata

Ingredients

• 10 ounces frozen spinach thawed
• 3 tablespoons unsalted butter
• 1 large finely chopped onion
• 4 cloves garlic
• 8 ounces mushrooms
• ½ teaspoon salt
• ½ teaspoon black pepper
• ¼ teaspoon grated nutmeg freshly
• 6 cups rosemarybread
• 6 ounces grated Gruyère coarsely
• 2 ounces parmigiano reggiano finely grated
• 2.8 cups milk
• 9 large eggs
• 2 tablespoons Dijon mustard