Heat olive oil in a skillet over medium heat.
Spread butter on one side of each slice of sourdough bread.
Place one slice of bread, butter side down, in the skillet.
Layer the shredded chicken evenly on the bread.
Spoon marinara sauce over the chicken, then sprinkle with mozzarella and Parmesan cheese.
Season with Italian seasoning, salt, and pepper.
Top with the second slice of bread, butter side up.
Cook for about 3-4 minutes until the bottom is golden brown, then carefully flip and cook for another 3-4 minutes until the other side is golden and the cheese is melted.
Remove from skillet, slice in half, and serve hot.