Preheat the oven to 400°F (200°C).
Melt 5 tablespoons of butter. Whisk in the garlic powder and chopped parsley.
Place the French bread halves on a baking sheet and brush the cut sides generously with the garlic butter.
Bake for 4–5 minutes, just until the bread is lightly golden and slightly crisp.
Meanwhile, add the remaining 3 tablespoons of butter to a saucepan over medium-low heat.
Add the Alfredo sauce, minced garlic, Parmesan cheese, onion powder, smoked paprika, salt, and black pepper. Stir gently until the sauce is hot, smooth, and well combined.
For the Chicken Alfredo Garlic Bread, spread half of the warm Alfredo mixture evenly over the toasted bread.
Arrange the chopped cooked chicken over the sauce.
Sprinkle the mozzarella evenly over the chicken, followed by the remaining Parmesan.
Bake for 8–10 minutes, or until the cheese is melted, bubbling, and lightly golden.
Let the bread rest for a minute or two, then slice and serve warm.