Preheat oven to 325 degrees F (165 degrees C).
Cook and stir beef and onion together in a large skillet over medium-high heat until the beef is browned and crumbly
5 to 7 minutes; drain and discard grease.
Stir ground beef mixture
sour cream
corn
mushroom soup
chicken soup
and egg noodles together in a large bowl; season with salt and pepper and spread the mixture into a 13x8-inch baking dish.
Bake in preheated oven until the egg noodles are tender
about 45 minutes. Sprinkle cheese over the top of the casserole and continue baking until the cheese is melted
