Preheat your oven to 425°F.
Trim and halve the Brussels sprouts; place them in a bowl.
In the bowl, toss the Brussels sprouts with olive oil, garlic powder, salt, and pepper.
Place the seasoned Brussels sprouts on a baking sheet, and roast them in the preheated oven for 20-25 minutes until they are tender and slightly crispy.
Meanwhile, season the chicken breast with salt and pepper on both sides.
Heat a skillet over medium-high heat and sear the chicken breast for 2-3 minutes per side until golden.
Transfer the chicken to an oven-safe dish and place it in the oven with the Brussels sprouts for an additional 10-12 minutes or until the chicken reaches an internal temperature of 165°F.
In a small saucepan, heat the balsamic vinegar over medium heat for 2-3 minutes until it slightly thickens to a glaze consistency.
Once the chicken is done, drizzle the balsamic glaze over the Brussels sprouts and chicken before serving.