Make the marinade: In a small bowl mix together 2 tablespoons balsamic vinegar, 1 1/2 tablespoons olive oil, 1 1/2 teaspoons garlic powder.
Marinate the chicken: Place the chicken breasts into a glass or ceramic bowl and pour the marinade over the chicken. Marinate for at least 30 minutes and up to overnight.
Prepare: Slice 20 cherry tomatoes in half, chop 1/4 cup fresh basil into strips and preheat the oven to 350°F.
Sear the chicken: Heat olive oil in a skillet over medium-high heat. Pat the chicken dry, then add to the hot skillet. Cook for 2–3 minutes per side until golden brown.
Bake: Add the cherry tomatoes, cover the pan and bake for 10 minutes.
Make the balsamic glaze: While the chicken cooks, heat ½ cup balsamic vinegar in a small saucepan over medium-high heat. Bring to a boil, then reduce heat and simmer, stirring occasionally, for about 10 minutes until thickened and syrupy.
Finish: Remove the pan from the oven, drizzle half of the glaze over the chicken, and top each piece with mozzarella. Return to the oven and bake uncovered until the cheese is melted and the chicken reaches 165°F.
Serve: Drizzle with the remaining balsamic glaze and garnish with fresh basil.
Notes
Use chicken breasts that are close in size for even cooking. If they are thick, pound them slightly before searing.
Pat the chicken dry before it goes into the skillet so it browns instead of steaming.
The balsamic glaze can go from perfect to too thick quickly, so remove it from the heat as soon as it turns syrupy.
Add the basil just before serving for the freshest flavor.