cowboy casserole :: 1 1/2 pounds ground beef + 1 medium onion, chopped + 3 cloves garlic, chopped + 1 can (15.25oz) whole kernel corn, drained + 1 can condensed cream of mushroom soup + 2 cups cheddar cheese, shredded + 1/2 cup milk + 4 tablespoons sour cream + 1 bag (30 oz) frozen tater tots (ore-ida crispy crowns)