Preheat your oven to 425℉ or your air fryer to 400℉. Line a small baking sheet with parchment paper.
Slice your chicken breast in half lengthwise almost to the end but keeping it intact as one piece of chicken. You want a flap or book type situation. Season the inside of each piece with salt and pepper to taste. Then add in 2 tablespoons of marinara to the interior of each piece and spread out. Next add in 1/3 of the mozzarella and top with 7 slices of pepperoni. Fold the chicken flap over and press down. Season the tops of the chicken with salt and pepper to taste.
Top Crust:
In a small bowl, whisk together the the grated parmesan and all spices until incorporated. Sprinkle this mixture evenly on all of the tops of the chicken breasts. Bake for 20-25 minutes in your oven or 18-20 minutes in your air fryer. Thickest part of chicken should have an internal temperature of over 165℉.