Preheat your oven to 400°F and line a large rimmed baking sheet with parchment paper.
Trim the woody ends off the Brussels sprouts and slice each one in half lengthwise.
Dice the chicken breast into uniform 1-inch cubes to ensure they cook at the same rate as the vegetables.
In a large mixing bowl, combine the halved Brussels sprouts and chicken cubes with olive oil, sea salt, black pepper, and garlic powder.
Toss thoroughly until everything is evenly coated, then spread the mixture in a single layer on the prepared baking sheet.
Roast for 20 to 25 minutes, tossing the ingredients halfway through, until the chicken is cooked through and the sprouts are tender with crispy edges.
While the tray is roasting, add the balsamic vinegar and honey to a small saucepan over medium-low heat.
Simmer the balsamic mixture for 3 to 5 minutes, stirring frequently, until it reduces by half and becomes a thick, syrupy glaze.
Remove the baking sheet from the oven and immediately drizzle the warm balsamic glaze over the chicken and sprouts before serving.