In a bowl of an electric mixer add artichoke hearts, spinach, onion, garlic, cream cheese, sour cream, mayonnaise, 1/2 cup of the Italian blend shredded cheese, and Parmesan cheese. Mix on low speed until smooth and combined. Set aside while you prepare the bread.
Hollow out the center of each half of the Italian bread.
Stuff each half with an equal amount of filling.
Sprinkle the remaining 1/2 cup Italian blend shredded cheese onto each half.
Cover bread loosely with foil and bake for 20 minutes until the filling is hot.
Remove the foil and let bake until the top of the cheese is golden brown, about 10 minutes more.
Let the bread rest for 5 minutes, slice, and enjoy!