In a bowl add cream cheese, butter, mayonnaise, garlic, drained spinach, artichoke hearts, both shredded cheeses and black pepper. Mix until combined.
1 block cream cheese, 8 Tablespoons unsalted butter, 1/4 cup mayonnaise, 3 cloves minced garlic, 10 ounces thawed, frozen spinach, 15 ounces artichoke hearts, chopped, 1/4 cup shredded mozzarella cheese, 1/4 cup shredded parmesan cheese, 3/4 teaspoon black pepper to taste