4 Tablespoons (1/2 stick) unsalted butter
2 large onions, chopped
1/4 cup all-purpose flour
1/4 teaspoon grated nutmeg
1 cup heavy cream
2 cups milk
1 teaspoon Dijon mustard
1 1/2 cup grated white cheddar cheese (divided, 1 cup for filling and 1/2 cup for topping)
3 pounds or 5 10-ounce bags frozen, chopped spinach, defrosted
1 cup grated Parmigiano-Reggiano (divided, 1/2 cup for filling and 1/2 cup for topping)
2 ½ teaspoons kosher salt
1 Tablespoon lemon juice
Preheat oven to 425°F.
Sauté Onions: In a large, heavy skillet, melt butter over medium heat. Add onions and sauté until translucent, about 10 minutes. Add flour and nutmeg and cook, stirring, for 2 more minutes. Add cream and milk and cook until thickened, about 2-3 minutes. Transfer to a bowl and add mustard and 1 cup of the cheddar.
Prepare Spinach: Squeeze out as much water as possible – put the spinach in the colander and press spinach with a plate or a can. Add spinach to onion/milk mixture. Add 1/2 cup of Parmigiano-Reggiano and mix well. Add kosher salt and lemon juice.
Bake Gratin: Transfer spinach to a buttered gratin dish and sprinkle remaining 1/2 cup Parmigiano-Reggiano and remaining 1/2 cup cheddar on top. Bake for 20 minutes. Broil for 3 more minutes or until top is lightly browned and bubbly. Serve immediately.
Recipe created by Parties That Cook®