Preheat the oven to 350 degrees F (175 degrees C). Grease a 9x13-inch casserole dish.
Mix Cheddar cheese, potato soup, sour cream, cream cheese, green onions, garlic, and salt together in a large bowl. Fold potatoes into mixture; pour into the prepared casserole dish. Top with Parmesan cheese.
Bake in the preheated oven until bubbling and cheese is golden brown, about 1 hour.
