Combine all of the ingredients and mix until well combined
10 ounces frozen chopped spinach, ½ cup light sour cream, ¾ cup low-fat Greek yogurt, ½ cup freshly grated Parmesan cheese, 8 ounces canned water chestnuts, 1 clove garlic, 1½ cups shredded low-fat mozzarella cheese, ⅛ teaspoon ground black pepper