Preheat your oven to 350°F (175°C).

Using a sharp bread knife, slice the sourdough loaf into strips in a diagonal pattern, making sure not to cut all the way through.

Make cuts in the opposite direction to create a crosshatch design, ensuring you do not cut through the bottom crust.

In a bowl, combine the chopped artichoke hearts, drained spinach, sour cream, cream cheese, half of the mozzarella, Parmesan cheese, garlic powder, salt, and pepper. Mix until smooth and well combined.

Gently stuff the spinach and artichoke mixture into the crevices of the cut bread, pressing it in deeply.

Sprinkle reserved mozzarella cheese on top of the bread, allowing some to fall into the crevices.

Wrap the stuffed loaf in foil and place it on a baking sheet.

Bake in the preheated oven for 10 minutes, then remove the foil and continue baking for another 10-15 minutes, or until the cheese is fully melted and bubbly.

Let the bread cool slightly, then serve warm. Pull apart pieces to enjoy the gooey, cheesy goodness!