Preheat oven to 350°F. Grease a 13x9 inch pan with cooking spray or butter.
Whisk together the corn muffin mix, butter, eggs, and salt.
Stir in drained corn kernels, cream style corn, and sour cream.
Pour the mixture into the greased 13x9 baking dish. Bake for 45–50 minutes, or until the center no longer jiggles when shaken, and the casserole is beginning to brown slightly on top. Serve immediately.
Notes
You can use a slightly smaller dish, such as an 11x9 inch pan, with good results. The casserole will be taller with a smaller dish. But a 13x9 inch pan, as written in the instructions, works great too! You can substitute 1½ cups of frozen corn (defrost it first) for the canned corn. Make it ahead: prepare the casserole as directed but don't bake it. Instead, cover it with plastic wrap or foil, and refrigerate for up to 24 hours. When you're ready to bake it, preheat the oven and bake as directed. You may need to add an additional 5 minutes because the casserole is cold. Freezing: prepare and bake the casserole as directed. Let it cool completely. Cover the casserole dish with a layer of plastic wrap, followed by a layer of foil. Freeze for up to 1 month. Defrost the casserole in the refrigerator for 24 hours. Then, bake in a 350°F oven for 18–22 minutes, or until warm throughout.