Add butter, egg and sour cream to a large mixing bowl and mix to fully combine. Add corn, creamed corn and cheddar cheese and mix to combine. Finally, sprinkle in jiffy corn muffin mix, garlic powder, onion powder and mix until fully combined.
Pour corn casserole mixture into a large lightly greased 13"x9" baking dish. Bake for about 50-55 minutes or until top is nice and golden. Remove from oven to let cool.
Serve corn casserole with your favorite main courses! Store leftovers in an airtight container in the fridge completely cooled for up to 2-3 days.