01 - Heat the oven to 350°F.
02 - Remove the top of the sourdough loaf and hollow out the inside, maintaining a 0.8–1.2 inch thick shell. Cube the removed bread for dipping.
03 - In a large bowl, blend cream cheese, sour cream, mayonnaise, Parmesan, mozzarella, garlic, onion, salt, pepper, and nutmeg until smooth.
04 - Fold the drained spinach into the cheese mixture thoroughly.
05 - Spoon the dip into the hollowed bread bowl and place it with the bread cubes onto a baking sheet.
06 - Bake for 25 minutes until the dip is hot, bubbling, and golden on top.
07 - Sprinkle chopped fresh chives on top if desired. Serve immediately with bread cubes for dipping.