01 -
Preheat your oven to 350°F and grease a 9x13-inch baking dish really well so nothing sticks.
02 -
Heat your oil or butter in a large skillet over medium heat. Add the sliced squash and chopped onions, then cook for about 10 minutes, stirring often, until the squash gets nice and tender. Drain off any extra liquid that builds up.
03 -
In a big bowl, mix together your cooked squash and onions with the cream soup, sour cream, shredded cheese, beaten egg, salt, and pepper. Stir everything until it's well combined and creamy.
04 -
Pour your squash mixture into the greased baking dish and spread it out evenly so it cooks uniformly.
05 -
In a small bowl, mix your crushed crackers with the melted butter until they're well coated. Sprinkle this mixture evenly over the top of your casserole.
06 -
Pop it in the oven for 35-40 minutes, until the top turns golden brown and you can see it bubbling around the edges. That's when you know it's perfectly done!