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Golden-brown butternut squash casserole in a white baking dish, topped with melted mozzarella cheese and fresh basil garnish

Butternut Squash Casserole


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  • Author: Inez Rose
  • Total Time: 50 minutes
  • Yield: One 9×13 casserole 1x

Description

This savory butternut squash casserole with creamy custard base and melted cheese is the perfect fall comfort food. Easy to make ahead and absolutely delicious!


Ingredients

Scale

For the Squash Base:

  • 2 tablespoons olive oil
  • 2 small onions, finely chopped
  • 1 medium butternut squash (about 2½ lbs), peeled, seeded, and cut into 1″ cubes
  • 6 garlic cloves, crushed
  • ¼ teaspoon salt (plus more to taste)
  • 1 tablespoon water (optional, if mixture gets too dry)

For the Custard Mixture:

  • 3 large eggs, lightly whisked
  • ¾ cup sour cream
  • 1 cup grated Parmesan cheese (or Grana Padano – they’re practically twins!)
  • â…“ cup chopped fresh basil (or 1 tablespoon dried)
  • ¼ teaspoon freshly cracked black pepper

For the Topping:

  • 8 oz shredded mozzarella cheese

Instructions

Step 1: Crank your oven to 425°F and butter up that 9×13″ dish. I grabbed mine from my mom’s kitchen years ago and conveniently forgot to return it.

Step 2: Dump the olive oil in your skillet over medium heat. Toss in those chopped onions and let them hang out for about 10 minutes until they smell like heaven and look all golden. This is when my kids start wandering into the kitchen asking what’s for dinner.

Step 3: Chuck in the butternut squash cubes, smashed garlic, and salt. Sometimes this gets dry and starts sticking – that’s when you splash in the water. Stir it around every few minutes for another 10 minutes until you can stab the squash with a fork easily. Don’t let it turn to mush or you’ll hate yourself later.

Step 4: Scrape all that goodness into your buttered dish and spread it around so it’s not all lumpy in one corner like I did the first time.

Step 5: Crack those eggs into a bowl and whisk in the sour cream, Parmesan, basil, and pepper. It looks gross at first but keep whisking until it’s smooth. Pour this over your squash and watch it settle into all the cracks.

Step 6: Dump that mozzarella on top. I always add more than I think I need because cheese makes everything better.

Step 7: Stick it in the oven for 30 minutes. You’ll know it’s done when the cheese is all bubbly and golden and your house smells so good the neighbors might knock.

Step 8: Let it sit for maybe 5 minutes before you dive in. I never wait long enough and always burn my tongue because I’m impatient.

Notes

Room temperature eggs mix easier – I set mine on the counter while I prep everything else. Cold eggs straight from the fridge create lumpy spots in the custard.

Skip the low-fat sour cream – I tried it once to be “healthier” and the whole thing turned out watery and bland. Full-fat is what makes this creamy and rich.

Fresh grated cheese melts like a dream – Pre-shredded has that coating stuff that makes it clump up. Takes two extra minutes but totally worth it.

Biggest mistakes I see: Oven temperature too low (your cheese stays pale and sad), overcrowding the pan during sauté (everything steams instead of browning), cutting squash pieces way too big (they stay crunchy in the middle).

  • Prep Time: 20 minutes
  • Cook Time: 30 minutes
  • Category: Side Dish
  • Method: Baked
  • Cuisine: American

Nutrition

  • Serving Size: 1/4 of casserole
  • Calories: 385 per serving
  • Sugar: 12g
  • Sodium: 680mg
  • Fat: 28g
  • Saturated Fat: 15g
  • Unsaturated Fat: 11g
  • Trans Fat: 0g
  • Carbohydrates: 22g
  • Fiber: 4g
  • Protein: 18g
  • Cholesterol: 195mg