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. I’d alternate it with this beautiful and delicious Stuffed Butternut Squash.

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 or using the shredding disk on your food processor 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!

Ingredients

• 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. You can also use the shredding disk on a food processor. 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. 

Possible Variations

• 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.