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

Instructions

1. Squeeze liquid from spinach and set aside.

2. Heat butter over medium heat and cook onion and mushrooms until soft.

3. Add 1/2 teaspoon of the salt and the pepper and nutmeg and cook for one minute.

4. And spinach, stir, and remove from heat.

5. In a lightly buttered 1 1/2 to 2 quart casserole, spread one third of the bread cubes across the bottom, then 1/3 of the spinach mixture, then 1/3 of the Gruyere, and 1/3 of the Parmesan.

6. Continue layering ingredients, finishing with a cheese layer.

7. Whisk together the milk, eggs, and mustard. Pour evenly over casserole.

8. Bake at 350 degrees for about 45 minutes, until golden brown and puffy in the middle. Casserole can be refrigerated overnight before cooking.