Wash the yellow squash under cool water. Use a knife and cutting board to slice the squash into thin, even pieces. This helps them cook evenly. Set the squash aside and boil about two quarts of water in a pot. Add the squash and cook for about 5 minutes, or until soft. Drain the squash in a colander and let it cool a bit before moving on.

In the same pan, heat a little butter over medium heat. Chop the onion into small pieces and add it to the pan. Cook the onion for 3–5 minutes, stirring often, until it gets soft and clear. This step gives the casserole extra flavor by making the onion sweet and tasty.

In a big bowl, mix the cooked squash and sautéed onions. Add sour cream, shredded cheddar cheese, and cream of chicken soup. Stir everything together until it’s well mixed. Add salt and pepper to taste. This creates the creamy base for your casserole.

Preheat your oven to 350°F (175°C). Grease a baking dish with butter or cooking spray. Pour the squash mixture into the dish and spread it out evenly. Sprinkle crushed Ritz crackers on top, then drizzle melted butter over the crackers. This will make the topping crispy and buttery.

Put the dish in the oven and bake for 25–30 minutes. It’s ready when the top is golden and the edges are bubbling. Take it out of the oven carefully and let it cool for about 5 minutes before serving. This helps the flavors come together and makes it easier to serve.

Scoop out portions with a serving spoon. Squash casserole tastes great with roasted meats, fresh salads, or even on its own. Add some herbs or extra cheese on top if you want to make it look fancy. Enjoy this warm, comforting dish!