This is a rich and creamy way to use up leftover marinara sauce or chicken. For an extra-Italian twist, use Italian sausage instead.
Preheat oven to 375°F. Stir together chicken, cream cheese, salt, pepper, 1 1/2 cups of the marinara, and 1 cup of the mozzarella in a medium bowl until combined. Spread mixture evenly in an 8-inch square casserole dish. Spread remaining 1/2 cup marinara evenly over chicken mixture; sprinkle with remaining mozzarella. Bake in preheated oven until cheese is melted, about 15 minutes.
While dip bakes, stir together panko, Parmesan, olive oil, and Italian seasoning. Sprinkle panko mixture evenly over dip, and bake until golden brown and bubbly, about 15 minutes. Let stand 5 to 10 minutes before serving. Garnish with fresh basil; serve with pita chips or crostini.