Heat olive oil in a skillet over medium heat.
In a bowl, mix the shredded chicken with marinara sauce, Italian seasoning, salt, and pepper.
Place one slice of sourdough bread in the skillet. Layer half of the mozzarella cheese on top.
Spoon the chicken mixture over the cheese, then sprinkle with the remaining mozzarella and Parmesan cheese.
Top with the second slice of sourdough bread. Cook for about 3-4 minutes until the bottom is golden brown.
Carefully flip the sandwich and cook for another 3-4 minutes until the other side is golden and the cheese is melted.
Remove from the skillet, let it cool slightly, and garnish with fresh basil if desired. Cut in half and serve.