01 - Preheat the oven to 350°F.
02 - In a large bowl, combine cream cheese, sour cream, mayonnaise, mozzarella, Parmesan, garlic, salt, pepper, and nutmeg. Mix until completely smooth and creamy.
03 - Add the drained spinach to the cheese mixture. Mix thoroughly until spinach is evenly distributed throughout the creamy base.
04 - Spoon the spinach mixture into the hollowed-out sourdough loaf. Alternatively, transfer to a small baking dish if preferred.
05 - Place the filled loaf or baking dish on a baking tray. Bake for 20-25 minutes until the dip is bubbling and the top develops a golden-brown color.
06 - Serve immediately while hot. Garnish with fresh herbs if desired. Use the hollowed-out bread pieces and additional sourdough slices for dipping.