In large pot with a steam basket, steam cauliflower florets and yams/sweet potatoes with about 1 inch of water in bottom of pot. Steam for 10 to 12 minutes, or when fork tender. Drain vegetables and add to a large mixing bowl. Using a potato masher, mash cauliflower and yams/sweet potatoes. Once mashed to your desired consistency, add the alfredo sauce, mozzarella and parmesan cheese.