Preheat oven to 350 deg.
Saute the squash and onion in the oil and butter until soft. Transfer to a bowl and then mix in parmesan, cheddar, sour cream and salt and pepper. Put in casserole dish.
Sprinkle crushed crackers on top. Cook for 30 minutes. Brit loves it!! Enjoy. I am not a cook and it is so easy and fast. Enjoy.