Making squash casserole requires an onion, butter, yellow squash, shredded cheese, and mayonnaise or sour cream. Additional ingredients include crackers, salt and pepper. Some recipes require oil to saute the squash, while others call for boiling the squash. Other ingredients that are sometimes used include sugar, eggs and Parmesan cheese.
For a squash casserole where the squash is sautéed, first heat 1 tablespoon vegetable oil in a skillet over medium heat. Add 6 thinly sliced yellow squash, a thinly sliced onion and 1 tablespoon butter to the skillet and cook until soft. Move the squash mixture to a bowl with 1/2 cup grated Parmesan cheese, 1 cup shredded cheddar cheese, 1/2 cup sour cream, and salt and pepper to taste. Put the cheese and squash mixture in a casserole dish and top with a sleeve of crushed crackers. Bake the casserole for 20 minutes at 350 degrees Fahrenheit.
For a recipe using boiled squash, add 3 pounds sliced yellow squash to a pot of boiling water and cook for eight to 10 minutes. Saute a small chopped onion and 4 tablespoons butter until the onion is soft. Combine the onion, squash, 1 cup shredded Cheddar cheese and two lightly beaten eggs, along with 1/4 cup mayonnaise, 2 teaspoons sugar and 1 teaspoon salt. Place the mixture in a greased baking dish and top with a mixture of cracker crumbs and melted butter. Bake for 30 to 35 minutes at 350 degrees Fahrenheit.