preheat oven to 400˚
lightly oil an ovenproof baking dish or skillet
prepare chicken breasts by slicing deeply but not through across the chicken breasts to make pockets for stuffing
mix the pepper, garlic, and salt together, and sprinkle over the breasts, rub it in well
divide the mustard between the breasts and rub it in
stuff the ham evenly in all the pockets of the chicken
then stuff half of the cheese in as well
place in the prepared dish or cast-iron skillet
bake at 400˚ for 20-25 minutes or until the chicken is almost cooked through, look for clear juices to drain
sprinkle the rest of the cheese over the chicken, divide the panko over the top of the chicken
put it back in the oven to brown up for about another 5 minutes
once it's browned it's done
slices and serve while hot