Begin by preheating your oven to 350°F. Lightly grease a small baking dish (about 1 quart in size) using non-stick cooking spray.
In a large bowl, combine the softened cream cheese, sour cream, and mayonnaise. Add the minced garlic, Parmesan, mozzarella, and a sprinkle of pepper, stirring until well-blended and smooth.
Fold in the chopped artichoke hearts and thawed spinach, ensuring the mixture is evenly incorporated.
Transfer the dip into the prepared baking dish, spreading it out evenly. Place in the preheated oven and bake for about 20 minutes, or until the dip is thoroughly warmed and the cheese is melted and bubbly.
Serve hot with your choice of tortilla chips, crackers, or toasted baguette slices for dipping.