Season chicken liberally with salt and pepper – about 1 teaspoon per pound of chicken.
Heat a large cast-iron or regular skillet to a medium heat. Add butter and olive oil. Once the butter melts, add the chicken. Sear until golden brown, about 5-6 minutes. Flip and sear until the other side is golden brown as well, another 5-6 minutes.
Add in the balsamic vinegar and chicken stock. Use a wooden spoon to scrape up all the brown bits at the bottom of the pan. Bring mixture to a boil and reduce to a simmer.
Layer chicken with a few mozzarella slices followed by a few tomato slices. Drizzle with a little bit of olive oil. Season tomato with salt and pepper.
Bake in the oven until the cheese is melted and the chicken has reached 165 degrees at the thickest part of the breast.
Remove from the oven and spoon sauce on top. Garnish with fresh basil leaves.
Use an oven safe skillet for this recipe so that you can easily transfer the chicken from the stovetop to the oven.
Use chicken breasts of a similar thickness so that they all cook through evenly.
Let the chicken rest for 5 to 10 minutes before serving to let the juices redistribute.