Creamy Butternut Squash and Spinach Casserole has just enough cream sauce between its layers to feel rich and festive. It’s a colorful vegetarian and gluten-free side dish that is perfect for the holidays.
I’ve been making a variation of this holiday side dish for as long as I can remember – sometimes at Thanksgiving and sometimes at Christmas. I was a vegetarian for many years and this beautiful layered casserole always felt special enough to be the main event for a vegetarian at the holidays. It was originally inspired by the Butternut Squash and Creamed-Spinach Gratin in Gourmet magazine. Over the years I’ve made a few small adjustments including increasing the parmesan cheese and reducing the sauce to get a more creamy layer, but the original idea remains the same.
If you’re not a fan of sweet potato casserole at the holiday or are looking for another colorful vegetable side dish, this is a great alternative.
Once the squash is sliced into thin disks (it’s worth pulling out a mandolin for this), the rest is easy to make. And it can be completely assembled up to 3 days ahead to just bake whenever you’re ready. Here’s how to make it!
- Butternut Squash – The key to the even, tender layers in the casserole is thinly sliced squash. If you have a mandolin, it’s worth getting it out to make quick and even work of slicing the squash. I only use my mandolin about twice a year and this is always one of my favorite ways to use it.
- Spinach – This works either with fresh or frozen spinach. If using frozen spinach, it can retain a lot of liquid, so defrost it first and squeeze as much moisture out as possible. Getting water out of the spinach is the key to a creamy (not watery) sauce.
- Onions and Garlic – These aromatics add to the richness of the dish. Be sure to chop them very fine so they just melt right into the sauce.
- Unsalted Butter – If using salted butter, be sure to reduce the additional salt you add.
- Heavy or Whipping Cream – Either heavy or whipping cream works to make the rich, creamy sauce.
- Parmesan Cheese – You’ll get the most smooth results if you grate this yourself, but pre-grated sauce will work.
- Salt, Pepper, Ground Nutmeg – Use these to season the dish.
How to Make Creamy Butternut Squash and Spinach Casserole Ahead
To prepare: Prepare the dish through the end of step 6, topping the casserole with parmesan and butter. Cover tightly with foil. Refrigerate for up to 3 days or freeze for up to 2 months.
To bake: To bake the dish, take it out of the fridge an hour before baking so that it comes to room temperature (if frozen, let it thaw in the fridge until fully defrosted). Bake as directed.
- Make it with different vegetables – This dish would be delicious made with thinly sliced sweet potatoes or Yukon gold potatoes in place of the butternut squash.
- Make it dairy-free – While not as rich, this dish is great when made with stock instead of cream. Or use a non-dairy milk alternative instead of cream. Saute the onions in olive oil and skip the parmesan.
- Bake it in ramekins – This is fun to bake in individual servings using ramekins or other small baking dishes.
My Complete Thanksgiving Menu
- Simple Roasted Turkey
- Bacon Wrapped Dates with Brie and Balsamic Honey (to serve as an appetizer)
- 1-Hour Light and Buttery Dinner Rolls
- Make-Ahead Mashed Potatoes
- Turkey Gravy with White Wine and Sage
- Homemade Green Bean Casserole
- Focaccia and Bacon Stuffing
- Creamy Butternut Squash and Spinach Casserole
- Cranberry Sauce (from Simply Recipes)
- Slow Cooker Pumpkin Cheesecake
Get more details and a complete Thanksgiving timeline here.
- Box Grater
- All Clad 5-quart Saute Pan
- 2 Quart Casserole Dish or 9″ Pie Plate or 9-inch Cake Pan
Creamy Butternut Squash and Spinach Casserole
- Saute Pan
- 2 qt Casserole Dish or 9" Cake Pan
- 1 cup finely diced White Onion
- 6 Tbsp Unsalted Butter, divided
- 4 cloves Garlic, finely chopped
- 1 tsp Kosher Salt
- 1/2 tsp Black Pepper
- 1/4 tsp Ground Nutmeg (preferably freshly grated)
- 8 oz Baby Spinach, roughly chopped
- 1 cup Heavy / Whipping Cream
- 1 cup grated Parmesan Cheese, plus extra for topping
- 1 3 lb Butternut Squash, peeled, seeds removed, and sliced into 1/8-inch slices
- Preheat oven to 350°F / 177°C. Spray a 2-quart casserole dish (or use a 9-inch pie plate or 9-inch cake pan) with nonstick cooking spray or brush with some oil.
- In a large saute pan over medium heat, melt 4 Tablespoons butter. Add onion and garlic and saute until onion is very soft, 7 to 8 minutes.
- To onion mixture, add salt, black pepper, nutmeg, and baby spinach. Saute until spinach is wilted (put the lid on to speed it along) and all of the liquid has cooked off, 7 to 8 minutes.
- Remove spinach from heat and whisk in heavy cream, parmesan cheese, and nutmeg.
- Layer squash and spinach-cream mixture, using about one fifth of squash and one fourth of spinach for each layer, beginning and ending with squash.
- Scatter parmesan cheese over top of casserole and dot with pieces of the remaining 2 Tablespoons of butter.
- If using a baking dish with shallow sides (like a pie plate) place it on a sheet pan to catch any liquid that bubbles over).
- Cover baking dish tightly with foil and bake until squash is nearly tender, 30 minutes.
- Remove foil and continue baking until casserole is golden brown on top and bubbling around the sides, about 15 minutes more.
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