Pin it The first time I made this casserole, I was snowed in for the weekend with a nearly-empty fridge and random ingredients that somehow worked together. That cold January afternoon, my kitchen filled with the most incredible aroma of roasting squash and sizzling sausage, and I remember standing by the oven just watching the cheese bubble through the glass door. Now whenever the weather turns crisp, I find myself craving those exact same cozy smells that made a snow day feel so comforting and complete.
Last autumn my sister came over for dinner after a terrible week at work, and I made this casserole without really thinking about it. She took one bite and literally stopped talking mid-sentence, then proceeded to eat three helpings while sitting at my counter in her work clothes. That moment of watching her shoulders actually drop and relax while she ate made me realize sometimes the simplest comfort food is exactly what someone needs.
Ingredients
- 1 medium butternut squash: Pick one that feels heavy for its size and has a matte skin. The sweetness of roasted squash is the backbone of this dish, so take the time to cut it into even cubes so everything roasts uniformly.
- 1 pound Italian sausage: I prefer sweet sausage here, but spicy adds a nice kick if that is your style. Removing the casing lets the meat crumble and cook evenly, distributing flavor throughout every bite.
- 1 medium onion: White or yellow onions both work beautifully here. Dicing them small helps them melt into the background and provide that savory base without overwhelming the other ingredients.
- 2 cloves garlic: Fresh garlic makes such a difference. Do not be tempted to use jarred minced garlic here, and let it cook just briefly so it does not turn bitter.
- 3 cups baby spinach: This wilts down dramatically, so do not be afraid of the large amount. It adds fresh color and a nice contrast to the heavier ingredients.
- 1 cup cooked quinoa: This adds protein and helps make the casserole more filling. Make it ahead of time or use leftover quinoa from another meal to save time.
- 1 cup shredded mozzarella: Freshly shredded cheese melts so much better than pre-shredded, which has anti-caking agents that prevent that perfect gooey texture we all want.
- ½ cup grated Parmesan: The salty, nutty flavor of Parmesan cuts through the richness and adds that umami depth that makes the whole dish taste more complex.
- 2 tablespoons olive oil: A good quality olive oil helps all the vegetables roast properly and adds a fruity background note.
- 1 teaspoon dried thyme: Earthy and slightly floral, thyme pairs perfectly with both the squash and the sausage.
- 1 teaspoon dried sage: Sage tastes like autumn in herb form. It adds that cozy, slightly piney flavor that makes this dish feel so comforting.
- 1 teaspoon paprika: Smoked paprika would add a lovely depth, but regular paprika works beautifully too for color and a mild peppery sweetness.
- Salt and pepper: Taste as you go, especially since the sausage and Parmesan both bring salt to the dish.
- 1 cup chicken or vegetable broth: This creates a little sauce as everything bakes, keeping the casserole from drying out while the flavors meld together.
- Fresh parsley: Completely optional, but a sprinkle of green on top makes the dish look so much more inviting and adds a fresh pop right before serving.
Instructions
- Get the oven ready:
- Preheat your oven to 375°F. Lightly grease a 9x13-inch baking dish with a little olive oil or cooking spray so nothing sticks later.
- Start the aromatics:
- Heat olive oil in a large skillet over medium heat. Add the diced onion and cook for about 5 minutes until it turns translucent and soft.
- Add the garlic:
- Throw in the minced garlic and cook for just 1 minute until fragrant. Do not let it brown or it will turn bitter.
- Brown the sausage:
- Crank up the heat slightly and add the sausage. Use a wooden spoon to break it apart as it cooks until browned and cooked through, about 7 to 10 minutes.
- Add the squash and spices:
- Stir in the butternut squash, thyme, sage, paprika, salt, and pepper. Let everything cook together for 5 to 7 minutes until the squash starts to soften.
- Add the spinach and quinoa:
- Throw in the baby spinach and cooked quinoa. Stir until the spinach wilts completely and everything is well combined.
- Create the sauce:
- Pour in the broth and let it simmer for 3 to 4 minutes. The liquid will start to thicken slightly as it combines with the starches from the quinoa.
- Assemble and top with cheese:
- Transfer everything to your prepared baking dish and spread it evenly. Sprinkle the mozzarella and Parmesan all over the top.
- Bake covered:
- Cover tightly with aluminum foil and bake for 25 minutes. This step steams the squash the rest of the way tender.
- Get it golden and bubbly:
- Remove the foil and bake for another 15 to 20 minutes until the cheese is melted, bubbling, and starting to turn golden brown in spots.
- Let it rest and serve:
- Let the casserole sit for 5 minutes before serving. This helps it set slightly so servings hold their shape better. Top with fresh parsley if you like.
Pin it This recipe has become my go-to for new parents, sick friends, or anyone who needs a meal that feels like a hug. Something about the combination of flavors and the way it fills the whole house with incredible smells just makes people feel cared for, which I think is the whole point of sharing food with people you love.
Make It Ahead
I love that I can assemble this entire casserole up to two days before baking it. Cover it tightly and keep it in the refrigerator, then add about 5 to 10 extra minutes to the covered baking time since it will be cold. This makes it perfect for dinner parties or busy weeknights when you want homemade food without the last-minute stress.
Vegetarian Option
When my vegetarian sister visits, I swap the sausage for two cans of drained white beans or use plant-based sausage crumbles. The casserole is just as satisfying and flavorful, and honestly, nobody misses the meat. The beans add a creamy texture that works beautifully with the squash and cheese.
Serving Ideas
This casserole is hearty enough to stand completely on its own, but a simple green salad with a bright vinaigrette cuts through the richness perfectly. Crusty bread for soaking up any extra sauce is never a bad idea either.
- A glass of light red wine like Pinot Noir complements the savory sausage beautifully.
- Leftovers reheat wonderfully and actually taste even better the next day as the flavors continue to develop.
- This freezes well for up to three months if you want to make a double batch and save one for later.
Pin it There is something so satisfying about a casserole dish that comes out of the oven bubbly and golden, and the way this one makes the whole house smell like comfort food is pretty unbeatable.
Recipe FAQs
- → Can I make this butternut squash casserole ahead of time?
Yes! You can assemble the entire dish up to 2 days in advance and refrigerate it. When ready to bake, add a few extra minutes to the cooking time since it will be chilled.
- → What can I substitute for the Italian sausage?
You can use plant-based sausage for a vegetarian option, or try regular ground pork or turkey with added Italian herbs. For a lighter version, chicken sausage also works well.
- → How do I store leftovers?
Store leftover casserole in an airtight container in the refrigerator for up to 4 days. Reheat individual portions in the microwave or cover the entire dish with foil and warm at 350°F until heated through.
- → Can I freeze this casserole?
Absolutely! Assemble the unbaked casserole, wrap tightly with plastic and foil, and freeze for up to 3 months. Thaw overnight in the refrigerator before baking as directed.
- → What other grains work in place of quinoa?
Cooked rice, couscous, or farro make excellent substitutes. Even orzo or small pasta shapes work—just adjust cooking liquid if needed and ensure grains are fully cooked before assembling.
- → How do I know when the squash is tender enough?
The squash cubes should easily pierce with a fork after the initial stovetop cooking. If they're still firm, continue cooking for a few more minutes before transferring to the baking dish.