2 pounds yellow squash, sliced ¼ inch thick
3 tablespoons unsalted butter, divided
1 tablespoon olive oil
¼ teaspoon garlic powder
½ cup sour cream
1 large egg, beaten
1 cup shredded cheddar cheese
½ cup grated Parmesan cheese, divided
¾ cup butter crackers, finely crushed
Salt and pepper, to taste
Add 1 tablespoon olive oil and 1 tablespoon butter to a large pot or Dutch oven. Melt over medium heat; once melted, add squash with a pinch of salt and pepper. Sauté for 8-10 minutes. Cover and continue cooking for 10-15 minutes, or until squash is fork tender. Remove pot from heat to allow squash to cool slightly before mashing.
Preheat oven to 350°F. Coat an 8×8-inch baking dish with cooking spray. Set aside.
Use a potato masher to mash squash. Add garlic powder, sour cream, butter, cheddar cheese, beaten egg, and ¼ cup Parmesan cheese. Continue to mash until all ingredients are well blended.
Pour squash mixture into prepared baking dish. Cover with cracker crumbs and ¼ cup Parmesan cheese. Drizzle over 2 tablespoons of melted butter. Bake covered for 35 minutes, then remove cover and finish baking 5-7 minutes, or until top is golden brown.