Prepare the chicken: Cook or grill chicken breasts until tender and slice or shred them. Toss the chicken with warmed Alfredo sauce.
Preheat the oven to 375°F (190°C).
Prepare the garlic bread subs: Slice the sub rolls open, leaving one side attached to create a pocket. In a small bowl, combine the melted butter, minced garlic, and parsley. Brush the inside of the sub rolls with the garlic butter mixture.
Stuff the rolls: Fill each roll with a generous portion of the chicken Alfredo mixture. Sprinkle Parmesan and mozzarella cheese on top.
Bake: Place the subs on a baking sheet and bake for 10-12 minutes, or until the bread is crispy and the cheese is melted.
Serve: Remove from the oven, garnish with extra parsley, and serve warm.