Melt the butter in a large skillet over medium heat.
Add the diced onion and minced garlic and sauté until the onion becomes soft and translucent.
Add the fresh spinach to the skillet a handful at a time, allowing it to wilt before adding more. Continue until all the spinach has cooked down, about 10–12 minutes total. Remove from heat and set aside.
In a large mixing bowl, combine the cream cheese, sour cream, and mayonnaise until smooth.
Stir in the Parmesan cheese, ground pepper, and chopped artichokes until well mixed.
Add the broth and stir until fully incorporated. The mixture will be slightly soupy — this is expected.
Fold in the spinach mixture and shredded mozzarella.
Spread the mixture evenly into a 4-quart baking dish and bake for 30 minutes, or until hot and bubbly.
Remove from the oven and serve immediately with crackers, tortilla chips, toasted French bread slices, bagel chips, or your favorite dippers. Enjoy!