In a small saucepan, combine balsamic vinegar and honey. Bring to a gentle boil over medium heat, then reduce to a simmer. Cook for 10-12 minutes until reduced by half and thick enough to coat the back of a spoon. It will thicken more as it cools. Set aside.

Pat chicken breasts dry and pound to an even 3/4-inch thickness using a meat mallet or heavy pan. Season both sides with 3/4 teaspoon salt, pepper, and garlic powder.

Heat olive oil in a large oven-safe skillet over medium-high heat until shimmering. Add chicken and cook undisturbed for 5-6 minutes until golden brown on the bottom. Flip and cook 4 minutes more. Chicken will not be fully cooked through yet.

Preheat broiler to high. Top each chicken breast with mozzarella slices. Transfer skillet to oven and broil for 2-3 minutes until cheese is melted and bubbly with light golden spots. Watch closely to prevent burning.

Remove from oven and immediately top with tomato slices and torn basil. Drizzle generously with balsamic glaze and sprinkle with remaining 1/4 teaspoon salt. Serve hot with extra glaze on the side.