Preheat your oven to 400 degrees f.
Lightly grease a baking dish with avocado oil or olive oil.
Pat your chicken dry using a paper towel.
To prepare the Hasselback chicken, cut into each chicken breast crosswise but not all the way through as shown in the photos.
Make about 5 slits in each breast that will fit your caprese fillings.
Season lightly with sea salt and pepper and add a big dollop of pesto sauce on each chicken breast.
Rub the sauce into the slits and on both sides to completely cover with the pesto, then transfer your chicken to your prepared baking dish in a single layer, cut side up, as shown.
Start assembling by inserting into the slits of your chicken one slice of mozzarella followed by one slice of tomato.
Bake for 25-30 minutes, or until the chicken has reached an internal temperature of 165 degrees f.
Garnish with fresh basil and serve while hot.