In a large bowl combine ½ cup Parmesan cheese, ½ cup heavy whipping cream, 8 ounces cream cheese, ½ teaspoon basil, ½ teaspoon salt, ½ cup yellow onion, 16 ounces cauliflower florets, 1 cup spinach, 2 tablespoons garlic, and 2½ cups chicken, except half of the 1½ cups mozzarella cheese. Reserve half of the cheese to top the casserole.
½ cup Parmesan cheese, ½ cup heavy whipping cream, 8 ounces cream cheese, ½ teaspoon basil, ½ teaspoon salt, ½ cup yellow onion, 16 ounces cauliflower florets, 1 cup spinach, 2 tablespoons garlic, 2½ cups chicken, 1½ cups mozzarella cheese