Preheat oven to 350 °F. Lightly coat a 9×13-inch baking dish with cooking spray. In a small bowl, combine cup mozzarella cheese and 1 Tbsp. Parmesan cheese. Set aside.
In a medium bowl, mix remaining mozzarella and Parmesan cheeses with cottage cheese. Set aside.
To boil, place sweet potato chunks in pan. Cover with water and bring to a boil. Cover pot and simmer until tender, about 15 minutes. Drain pot, then mash sweet potatoes and combine with salt.