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Easy make ahead Spinach Gratin being served.

Easy Make-Ahead Spinach Gratin

Easy Make-Ahead Spinach Gratin is full of creamy, cheesy goodness. Frozen spinach is mixed with a classic Mornay sauce accented with caramelized onions. It's topped with both Gruyère cheese and freshly grated Parmesan cheese to create an unforgettable dish. 
5 from 10 votes
Prep Time 15 minutes
Cook Time 20 minutes
Total Time 35 minutes
Course Side Dish
Cuisine American
Servings 6 servings
Calories 201 kcal

Ingredients
  

  • 24 ounce package frozen chopped spinach, thawed
  • 2 Tablespoons unsalted butter
  • 2 cups finely chopped onion (1 large onion)
  • 2 Tablespoons all-purpose flour
  • 1 teaspoon Kosher salt
  • ¼ teaspoon freshly ground black pepper
  • ⅛ teaspoon freshly grated nutmeg (See Tip 1)
  • 1 ½ cups milk (See Tip 2)
  • ½ cup (2 ounces) freshly grated Parmesan cheese, divided
  • ½ cup shredded Gruyère cheese

Instructions
 

  • Preheat oven to 425°F. Spray a 2-quart casserole dish with non-stick spray. Set aside.
  • By the handful, squeeze as much water as possible from the spinach. Repeat with paper towels. Set aside. 
  • Melt the butter in a large skillet over medium heat. Add the onions and sauté until lightly browned about 15 minutes. Add the flour, salt, pepper, and nutmeg. Cook, stirring, for 2 more minutes. Add the milk and cook until thickened. Add ¼ cup of grated Parmesan cheese. Stir until melted. Add the spinach; mix well.
  • Transfer to the prepared casserole dish. Top with Gruyère cheese and remaining Parmesan cheese. May be prepared in advance up to this point. (See Tip 3)
  • Bake in preheated 425°F oven for 20 minutes or until hot and bubbly.
  • Yield: 6 servings. (See Tip 4)

Video

Tips/Notes

  1. I like to use fresh nutmeg. However, you can also use ground nutmeg in this dish.
  2. I used whole milk, but feel free to use 2% milk.
  3. You can prepare this in advance for up to a day. Cover the casserole dish with aluminum foil and refrigerate. Add 5 minutes or so cooking time to compensate for the fact that the Spinach Gratin is cold from the refrigerator.
  4. The leftovers are as good, if not better. I generally just heat the leftovers for several minutes in the microwave.

Nutrition

Calories: 201kcalCarbohydrates: 15gProtein: 12gFat: 11gSaturated Fat: 7gCholesterol: 30mgSodium: 651mgPotassium: 565mgFiber: 4gSugar: 6gVitamin A: 13652IUVitamin C: 10mgCalcium: 397mgIron: 2mg
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