Preheat oven to 400º, I put the refrigerated sauce in a 9″ x 13″ baking dish during the preheat to warm up the sauce.
Make chicken: Prepare breading station with three large mixing bowls: one bowl with panko, garlic powder, and Parmesan mixed with a fork; another with the egg mixture; and the third bowl with flour. Season chicken with salt and pepper, then coat each piece of chicken in flour and shake off excess. Dip chicken into egg mixture and then into bread crumb mixture; repeat steps for remaining chicken and set aside on a plate.
In a deep cast-iron skillet over medium-high heat, add 1/4″ oil. When pan is hot but not smoking, add chicken. Cook until golden brown, 5 to 7 minutes, flipping halfway through. Transfer to a paper towel-lined plate to drain.
Once the oven is preheated, remove the pan with heating sauce.
Place chicken in sauce. Top with mozzarella and bake until cheese is melted, 10 to 12 minutes. If desired, broil until cheese is golden, 3 minutes.