Preheat the oven to 375°F.
Pound the chicken breasts to even thickness, if needed. Season lightly with salt and black pepper.
On a plate mix together ½ cup Parmesan, Italian seasoning, garlic and red pepper flakes. Coat chicken pieces on all sides, repeating until all is used.
On the stovetop heat a few drizzles of olive oil in a large 12-inch cast iron skillet or similar oven safe skillet over medium-high heat. Brown the chicken for 2 minutes per side. Remove from stovetop.
Pour pizza sauce over chicken. Top each with 3-4 pieces of pepperoni.
Sprinkle with mozzarella cheese and remaining Parmesan. Arrange remaining pepperoni on top. (May use more pepperoni, if desired)
Bake for 20-25 minutes or until chicken is cooked through and cheese is bubbly.
Rest for 5 minutes and serve with pasta or on toasted hoagie rolls.