In a large mixing bowl, combine the shredded chicken, basil pesto, mozzarella cheese, sun-dried tomatoes, red onion, olive oil, salt, and pepper. Mix well until all ingredients are evenly coated with pesto.
Slice the Italian bread lengthwise, creating a top and bottom half. Carefully hollow out some of the insides of the bread to create space for the filling.
Spoon the chicken and pesto mixture generously into the hollowed-out bread, ensuring it’s nicely packed.
Place the stuffed bread halves on a baking sheet and wrap them in aluminum foil to prevent burning.
Bake in the preheated oven for 25-30 minutes, or until the bread is crispy and the filling is hot and bubbly.
Remove from the oven, unwrap the foil, and let it cool for a few minutes.
Cut the stuffed bread into individual servings, garnish with fresh basil leaves, and serve warm.