Make the balsamic reduction. Add balsamic vinegar and brown sugar to a small saucepan over medium heat. Bring to a slight boil and reduce by half, about 6-8 minutes; set aside and let cool.
Heat olive oil in a medium skillet over medium high heat.
Season chicken breasts with salt and pepper, to taste. Add to skillet and cook, flipping once, until cooked through, about 3-4 minutes per side. Let cool before dicing into bite-size pieces.
To assemble the salad, place romaine lettuce in a large bowl; top with chicken, mozzarella, tomatoes, avocado and basil. Pour balsamic reduction on top of the salad and gently toss to combine.
Serve immediately.
Recipe Notes
Recipe adapted from Damn Delicious (Caprese Avocado Salad)