Spinach Gratin

Makes 8 servings

• 3 POUNDS FROZEN CHOPPED SPINACH, DEFROSTED (5 (10-OUNCE) PACKAGES)
• 4 TABLESPOONS (1/2 STICK) UNSALTED BUTTER
• 1 CHOPPED YELLOW ONION
• 1/4 CUP FLOUR
• 1/4 TEASPOON GRATED NUTMEG
• 1 CUP HEAVY CREAM
• 2 CUPS MILK
• 1 CUP FRESHLY GRATED PARMESAN CHEESE
• 1 TABLESPOON KOSHER SALT
• 1/2 TEASPOON FRESHLY GROUND BLACK PEPPER
• 1/2 CUP GRATED GRUYERE CHEESE

1. Transfer your thawed spinach to a large baking dish or bowl. Set aside.
2. Preheat the oven to 425 degrees F.
3. Melt the butter in a heavy-bottomed saute pan over medium heat.
4. Add the onions, and saute until translucent, about 15 minutes.
5. Add the flour and nutmeg and cook, stirring, for 2 more minutes.
6. Add the cream and milk, and cook until thickened.
7. Squeeze as much liquid as possible from the spinach, and add the spinach to the sauce. Add 1/2 cup of the Parmesan cheese and mix well. Season, to taste, with salt and pepper.
8. Transfer the spinach to a baking dish, and sprinkle the remaining 1/2 cup Parmesan and the Gruyere on top. Bake for 20 minutes until hot and bubbly. Serve hot.