Place ¾ of the stick of butter in a small pan, along with the spinach and minced garlic. Chop the artichoke hearts and add to the mixture. Let that sauté for just a minute while you cut the bread.
Cut bread loaf lengthwise and widthwise (without cutting all the way through the bottom of the loaf), creating approximately 1-inch wide sections of bread.
Place bread on a foil-lined baking sheet, stuffing the shredded mozzarella. Then, stuff in the sauteed spinach and artichokes.
Lightly spray foil with non-stick spray and wrap bread completely in foil. Bake at 350 degrees for 15 minute
While that bakes, melt the rest of the butter and in a small bowl, combine melted butter & garlic powder.
Remove from oven and unwrap the bread. Using a pastry brush, apply a light coat of the garlic butter mixture all over the bread. Sprinkle all over with Parmesan cheese.
Return to oven (bread unwrapped) and bake 10 more minutes (until cheese is melted and bread starts to look golden).