Why You’ll Love This Recipe

I love how this casserole brings together creamy, cheesy, and crunchy textures all in one bite. The butternut squash becomes tender and slightly sweet, which balances perfectly with the savory kale filling and that crispy, golden topping. It’s also a great make-ahead dish, which makes hosting a breeze. And although it tastes rich and decadent, it’s packed with nutrient-dense ingredients like kale, walnuts, and squash.

Ingredients

(Here’s a tip: Check out the full list of ingredients and measurements in the recipe card below.)

4 Tbsp. extra-virgin olive oil, divided
1 medium yellow onion, finely chopped
5 garlic cloves, minced
1/4 to 1/2 tsp. crushed red pepper flakes (I adjust based on how spicy I want it)
1 bunch lacinato kale, stems and ribs removed, chopped
1 cup heavy cream
1/3 cup, plus 2 Tbsp. grated Parmesan cheese, divided
1 Tbsp. Dijon mustard
1 Tbsp. fresh thyme leaves
3/4 tsp. kosher salt
1/2 tsp. black pepper
2 lbs. peeled and cubed butternut squash
1/2 cup shredded Gruyere or gouda cheese
2 cups torn or roughly chopped sourdough bread
1/3 cup finely chopped walnuts

Directions

I preheat the oven to 425ºF and grease a 3-quart baking dish.
In a large sauté pan, I heat 2 Tbsp. of olive oil over medium heat. I cook the chopped onion for about 7 to 8 minutes until soft, then stir in the garlic and crushed red pepper flakes and cook for 2 more minutes.
I add the chopped kale to the pan and cook until it softens, about 2 to 3 minutes. Then I stir in the heavy cream, 1/3 cup of Parmesan, Dijon mustard, thyme, salt, and pepper. I let it simmer for 3 to 5 minutes until it thickens slightly.
I arrange the butternut squash cubes in the prepared baking dish and pour the kale mixture over top, making sure it settles into all the gaps. Then I sprinkle the Gruyere evenly over everything.
I cover the casserole with foil and bake for 30 minutes. If the squash isn’t almost fork-tender by then, I give it another 10 minutes.
While that’s baking, I mix the sourdough, walnuts, remaining Parmesan, 2 Tbsp. olive oil, and a pinch of salt in a bowl. I gently massage the oil into the bread until everything’s well-coated.
I take the casserole out of the oven, discard the foil, and scatter the sourdough topping over the dish. Then I bake it uncovered for 20 more minutes, until the squash is tender and the top is golden.
I let it rest for 5 to 10 minutes before serving—it helps the filling set and makes it easier to scoop.

Servings and timing

This casserole serves 8 people, making it perfect for gatherings or meal prep for the week.

Prep Time: 20 minutes
Cook Time: 35 minutes (plus 10 if needed)
Total Time: About 1 hour

Variations

I sometimes use baby spinach instead of kale if that’s what I have on hand.
For a smokier flavor, I swap the Gruyere for smoked gouda.
If I want to make it vegan, I use plant-based cream and cheese alternatives, and a sturdy sourdough with olive oil only.
A sprinkle of nutmeg or a drizzle of truffle oil can elevate it for special occasions.
When I need it gluten-free, I use gluten-free bread for the topping and double-check all other ingredients.

Storage/Reheating

I keep leftovers in the fridge in an airtight container for up to 5 days.
To reheat, I use the oven at 350ºF to keep that topping crispy, but if I’m short on time, the microwave works fine too.
I also freeze portions in freezer-safe containers for up to 3 months. I just thaw them in the fridge overnight before reheating in the oven.

FAQs

Can I make this casserole ahead of time?

Yes, I often prep the squash and kale in advance. I can also assemble the casserole earlier in the day and bake it just before serving.

What kind of bread works best for the topping?

I like using a crusty sourdough for the best texture. Day-old bread works especially well because it holds up to the moisture.

Can I use frozen butternut squash?

I’ve used frozen squash before, but I let it thaw and drain it well first. Otherwise, it adds too much moisture and changes the texture.

What’s the best cheese substitute if I don’t have Gruyere?

Gouda is my favorite alternative, but sharp white cheddar also works great and adds a nice bite.

Can I leave out the walnuts?

Definitely. If I’m cooking for someone with a nut allergy or just want a simpler topping, I skip the walnuts or replace them with sunflower seeds.

Conclusion

Cheesy Butternut Squash Casserole is everything I want in a comfort-food side dish—rich, hearty, and layered with flavor. The creamy kale filling and cheesy squash make it cozy, while the sourdough-walnut topping gives it the crunch I crave. Whether I’m hosting or just making dinner feel a little more special, this casserole always hits the mark.

Cheesy Butternut Squash Casserole

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Author: Mia
Total Time: 1 hour
Yield: 8 servings
Diet: Vegetarian

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Description

This comforting butternut squash casserole is layered with creamy Parmesan kale, nutty Gruyere, and a golden walnut-sourdough topping—perfect for cozy dinners or festive gatherings.

Instructions

Preheat oven to 425ºF and grease an 11×7 or 13×9-inch baking dish.

Heat 2 Tbsp. olive oil in a large sauté pan over medium heat. Add onion and cook 7–8 minutes until soft. Add garlic and red pepper flakes; cook 2 more minutes.

Add kale and cook 2–3 minutes until softened. Stir in heavy cream, 1/3 cup Parmesan, Dijon, thyme, salt, and pepper. Simmer until thickened, about 3–5 minutes.

Arrange cubed butternut squash in prepared dish. Pour kale mixture over, stirring to coat. Top with shredded Gruyere.

Cover with foil and bake for 30 minutes, or until squash is nearly fork-tender. Add 10 more minutes if needed.

Meanwhile, mix sourdough, walnuts, 2 Tbsp. Parmesan, 2 Tbsp. olive oil, and a pinch of salt in a bowl. Toss until well coated.

Remove foil, scatter topping over casserole, and bake uncovered for 20 more minutes, until golden and squash is fully tender.

Let sit 5–10 minutes before serving.

Notes

To Make Ahead: Cube butternut squash up to 3 days in advance and store in an airtight container. Kale can be stemmed and chopped up to 1 day ahead.

To Store: Refrigerate leftovers, tightly covered, for up to 5 days.

To Reheat: Best reheated in the oven at 350ºF. Microwave if needed for convenience.

To Freeze: Freeze in a freezer-safe container for up to 3 months. Thaw overnight in the fridge and reheat at 350ºF.

Prep Time: 20 minutes
Cook Time: 35 minutes
Category: Side Dish
Method: Baking
Cuisine: American