01 - Preheat your oven to 375°F.
02 - In a medium skillet, sauté the minced garlic over medium heat for 1 minute until fragrant. If using fresh spinach, add it to the skillet and cook until wilted; if using thawed frozen spinach, ensure it's squeezed dry and skip this sauté step.
03 - In a large mixing bowl, combine the softened cream cheese, sour cream, and mayonnaise. Whisk until the mixture is smooth and well-incorporated.
04 - Fold in the drained and chopped artichoke hearts, the prepared spinach, 3/4 cup of the shredded mozzarella, the grated Parmesan, kosher salt, freshly ground black pepper, and crushed red pepper flakes (if desired). Mix thoroughly to combine all ingredients.
05 - Transfer the dip mixture into a 1-quart baking dish. Gently smooth the top surface and sprinkle evenly with the remaining 1/4 cup of shredded mozzarella cheese.
06 - Bake in the preheated oven for 20 to 25 minutes, or until the dip is heated through, visibly bubbly around the edges, and the top is lightly golden brown.
07 - Allow the baked dip to cool for 5 minutes before serving to prevent burns. Serve warm alongside tortilla chips, slices of toasted baguette, or an assortment of fresh vegetable crudités.