Heat olive oil in a skillet over medium heat.
Spread marinara sauce on one slice of sourdough bread.
Layer the shredded chicken on top of the marinara sauce.
Sprinkle the mozzarella and Parmesan cheeses over the chicken.
Season with Italian seasoning, salt, and pepper.
Top with the second slice of sourdough bread.
Melt butter in the skillet, then place the sandwich in the skillet.
Cook for 3-4 minutes on each side, or until the bread is golden brown and the cheese is melted.
Remove from the skillet, slice in half, and serve hot.