This is one of my favorite Ina Garten (who else?) recipes; everyone seems to love it, even spinach-haters. The recipe is extremely forgiving - you can use all whole milk, or cream, or half-and-half, or combinations of all the above. Just do NOT use skim or low fat milk, because the recipe won't work. You can add extra spinach, or even make the dish with a combination of spinach and swiss chard (sautee the stems, first).
Ina Garten uses a LOT of onions - four cups. I cut this amount in half. I also elminate the gruyere and double up on the parmesan cheese (the real stuff, please!). And I rarely make the recipe with cream, unless it is for a very special occasion.
Finally, it is critical that you get as much water as possible out of the spinach, so use cheese cloth or a potato ricer to do that. The more water you get out (admittedly, a time-consuming and messy procedure), the more sauce will soak into the spinach, and you won't have a watery mess at the bottom of the dish. Below is Ina's orginal recipe, without my tweaking!
Serves: 8 according to the book, but these are huge servings. I made this for Thanksgiving once, and it served 12, including seconds.
4 tbsp. unsalted butter
2 cups chopped yellow onions
1/4 cup flour
1/4 teaspoon freshly grated nutmeg
1 cup half-and-half
2 cups milk
About 3 pounds frozen chopped spinach ( five 10 oz. boxes), defrosted and squeezed to remove as much water as possible
1 and 1/2 cups grated Parmesan cheese
1 tbsp. kosher salt
1/2 tsp. freshly ground black pepper
Preheat oven to 425°F.
Melt the butter in a heavy bottomed pan over medium heat. Add the onions and sauté until translucent, about 15 minutes. Add the flour and nutmeg and cook, stirring, for 2 more minutes.
Add the cream and milk and cook until mixture has thickened.
Squeeze as much liquid as possible from the spinach and add the spinach to the sauce. Add 1 cup of the Parmesan cheese and stir well. Season to taste with the salt and pepper.
Transfer the spinach to a baking dish and sprinkle the remaining 1/2 cup of cheese on top. Bake for 20 minutes or until hot and bubbly. Serve immediately.
Ina Garten notes that the dish can be assembled with the cheese topping a day or two before the baking and baked before serving. She also says that, in this dish, the taste difference between frozen and fresh spinach is negligible, not worth the extra work, and I agree.