Preheat oven to 375°F. Defrost spinach in a strainer under warm water. Squeeze all excess moisture out using paper towel. Drain artichokes on a paper towel before chopping.
In a medium mixing bowl, combine cream cheese, sour cream, mayonnaise, garlic, pepper, and nutmeg with a hand mixer until fluffy.
Fold in artichokes, spinach, parmesan cheese, and 1 cup of mozzarella. Spread mixture into a 9x9" baking dish. Top with remaining mozzarella cheese.
Bake for 25-30 minutes or until mixture is hot and bubbly and cheese is fully melted. Allow to cool for 5 minutes before serving.