01 - Set the oven to 350°F (180°C) and allow it to fully heat.
02 - Combine cream cheese, sour cream, and mayonnaise in a large mixing bowl; stir until smooth and uniform.
03 - Add the drained spinach, minced garlic, sliced green onions, grated Parmesan, shredded mozzarella, salt, black pepper, optional nutmeg, and chili flakes; fold gently until ingredients are thoroughly combined.
04 - Transfer the mixture into a lightly greased baking dish or ovenproof skillet, spreading evenly.
05 - Place the dish in the oven and bake for 20 minutes or until the dip is bubbly and golden on top.
06 - Allow the dip to cool slightly before serving; present warm alongside crackers, bread, or fresh vegetables.