01 - Set oven to 350°F to prepare for baking.
02 - In a large bowl, blend cream cheese, sour cream, and mayonnaise until smooth.
03 - Stir in Parmesan, mozzarella, minced garlic, spring onions, salt, pepper, and nutmeg until evenly distributed.
04 - Fold in the thoroughly drained spinach, mixing gently until combined.
05 - Spread the mixture evenly into a baking dish suitable for the oven.
06 - Bake for 20 minutes until heated through, bubbling, and lightly browned on top.
07 - While baking, arrange sourdough cubes or slices attractively on a serving platter.
08 - Present the hot spinach dip immediately alongside the sourdough for dipping.