Creating this dip is straightforward and rewarding. Follow these steps to achieve a delectable and creamy result:

1. Preheat your oven to 375°F (190°C). This ensures that the dip bakes evenly and develops a nice golden top.
2. Prepare the spinach: If using fresh spinach, blanch it in boiling water for about 2 minutes, then transfer it to an ice bath to stop the cooking process. Drain and chop the spinach finely. If using frozen spinach, ensure it is thoroughly thawed and squeezed to remove excess moisture.
3. Mix the base ingredients: In a large bowl, combine the softened cream cheese, sour cream, and mayonnaise. Mix until the ingredients are well blended and smooth.
4. Add cheeses and seasonings: Stir in the Parmesan cheese, mozzarella cheese, minced garlic, salt, black pepper, and red pepper flakes (if using). Mix until everything is evenly distributed.
5. Incorporate spinach and artichokes: Fold in the chopped spinach and artichoke hearts, ensuring they are well integrated into the creamy mixture.
6. Transfer to a baking dish: Spoon the mixture into a 9-inch round baking dish or any similar-sized oven-safe dish. Spread it evenly across the surface.
7. Bake: Place the dish in the preheated oven and bake for 25-30 minutes, or until the top is golden brown and the dip is bubbly around the edges.
8. Cool slightly: Allow the dip to cool for a few minutes before serving. This helps the flavors meld together and makes it easier to scoop.