In a bowl, whisk together all the sauce ingredients: balsamic vinegar, honey, oil, minced garlic, Italian seasoning, and Dijon mustard. Season with salt and pepper to taste before setting it aside.

In another bowl, combine the halved grape tomatoes, mozzarella balls, and chopped basil. Season this mixture with salt and pepper as well before setting it aside.

Preheat your oven to 400 degrees F while preparing your chicken.

In a large oven-safe skillet over medium-high heat, heat some avocado oil until shimmering. Season both sides of the pounded chicken breasts generously with salt and pepper before placing them in the skillet in a single layer. Sear each side for about 1–2 minutes until lightly golden brown.

Once seared, pour the prepared balsamic sauce over the chicken in the skillet. It should start to simmer right away; use a wooden spoon to scrape up any brown bits from the bottom of the pan.

Remove the skillet from heat and sprinkle the tomato-mozzarella mixture evenly over the top of your chicken. Bake uncovered for about 18–23 minutes until your chicken reaches an internal temperature of 165 degrees F. Let it rest for about five minutes after removing it from the oven.