**Prepare the Garlic Bread:**
Preheat your oven to 400°F (200°C). In a small bowl, mix softened butter, minced garlic, and chopped parsley. Spread this mixture evenly over the cut sides of the bread. Sprinkle 1/2 cup shredded mozzarella cheese on top.
**Toast the Bread:**
Place the bread halves on a baking sheet, garlic side up. Bake for 5-7 minutes, or until the edges are golden and the cheese is melted. Remove from the oven and set aside.
**Prepare the Filling:**
In a mixing bowl, combine cooked chicken, marinara or Alfredo sauce (if using), 1 cup mozzarella cheese, Parmesan cheese, and Italian seasoning. Mix until well coated.
**Assemble the Sandwich:**
Spoon the chicken mixture evenly over one half of the toasted garlic bread. Place the other half of the garlic bread on top to form a sandwich.
**Heat the Sandwich:**
Heat a large skillet or grill pan over medium heat. Place the assembled sandwich in the skillet and cook for 3-4 minutes on each side, pressing down gently, until the filling is hot and the bread is crisp.
**Serve:**
Slice the sandwich into portions and serve immediately.