Preheat your oven to 400°F and line a large rimmed baking sheet with parchment paper.
Trim the ends off the Brussels sprouts and cut them in half, then dice the chicken breast into uniform 1-inch pieces.
In a large mixing bowl, combine the chicken and sprouts with the olive oil, sea salt, black pepper, and garlic powder, tossing until everything is well coated.
Spread the mixture in a single layer on the prepared baking sheet, ensuring the sprouts are cut-side down for maximum browning.
Roast for 20 to 25 minutes, or until the chicken is cooked through and the sprouts have developed a deep, crispy char.
While the tray is roasting, combine the balsamic vinegar and honey in a small saucepan over medium-low heat, simmering for 3 to 5 minutes until it reduces into a thick glaze.
Remove the tray from the oven and immediately drizzle the warm balsamic glaze over the chicken and sprouts before serving.