Pre-heat oven to 425F degrees
Wash and trim each breast, dry with a paper towel. Make a pocket-like cut on the side of the chicken (the long way). Do not cut through, all you need is a little opening
Season the breasts on both sides including the inside pocket.
While you are quick prepping the chicken, make sure to heat your cast iron with olive oil.
Place two asparagus inside of each breast. Let the asparagus hang of the ends. Stuff the breast with and a handful shredded cheese (this is literally how I measure things!). You can’t go wrong here, so add more or less depending on your preference.
Place stuffed chicken breasts top side down in the heated cast iron and sear for 3-4 minutes on each side.
Transfer the cast iron to the pre-heated oven and bake for 20 minutes.
Remove chicken from oven. This is a good time to check and see if the chicken is cooked through (internal temperature of 165F). Spoon some marinara sauce on top the chicken and top it with mozzarella cheese.
Bake for another 2-3 minutes just enough time to melt the cheese.
Remove from oven and serve with fresh parsley and grated cheese.