• Preheat oven to 400ºF. Spray a large baking dish with nonstick spray.

Stuff the Chicken:

• Add olive oil, salt, pepper, garlic powder, and Italian seasoning to a bowl, and whisk to combine.
  ½ tablespoon olive oil, ½ teaspoon kosher salt, 2 teaspoons garlic powder, 2 teaspoons Italian seasoning, ½ teaspoon ground black pepper
  
• Butterfly each chicken breast: cut ⅔ way through horizontally, but do not cut all the way through.
  4 boneless, skinless chicken breasts
  
• Evenly distribute the seasoning mix between the 4 chicken breasts, and rub to fully coat both sides.
  
• Take one chicken breast and open to expose the inside of the butterfly cut.
  
• Place a slice of mozzarella inside each chicken breast, then top with 5 slices of pepperoni. Add a spoonful of marinara and then top with a sprinkle of grated parmesan.
  4 slices thick-cut mozzarella cheese, 30 slices pepperoni, ⅛ cup freshly grated parmesan cheese
  
• Secure chicken breasts with toothpicks if needed.
  

Bake:

• Pour half of the marinara into the bottom of the baking dish and spread into a thin layer.
  24 ounces marinara sauce
  
• Arrange stuffed chicken breasts in the baking dish, directly in the marinara.
  
• Top the chicken breasts with the rest of the marinara and use a spoon to make sure the breasts are fully covered.
  24 ounces marinara sauce
  
• Top the marinara with the shredded mozzarella, remaining pepperoni, and remaining grated parm. Sprinkle with more Italian seasoning if desired.
  30 slices pepperoni, 1 cup freshly shredded mozzarella cheese, ⅛ cup freshly grated parmesan cheese
  
• Bake for 25 minutes, or until the internal temperature of the chicken reaches 165°F.