Prepare a baking sheet lined with parchment paper while preheating the oven to 400°F.
Slice 4-5 deep cuts in the chicken breasts, just enough to fit the tomato, basil, and mozzarella filling. Dredge each side of the breast with some black pepper and sea salt. Lay on the lined baking sheet.
Chop the tomatoes and mozzarella into thin portions. Insert a slice of tomato, mozzarella, and a basil leaf in the slits of the chicken breast.
Sprinkle the vinegar and olive oil onto the chicken.
Place in the oven for 20-25 minutes or wait until the chicken is cooked through.
While baking, chop the remaining basil leaves into strips.
Once the chicken is cooked, remove from the oven and garnish with the chopped basil leaves. Serve.
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Notes
If you want to reduce more carbs, replace balsamic vinegar with apple cider vinegar.