Preheat your oven to 400°F (200°C) and line a baking sheet with parchment paper.
Trim the ends of the Brussels sprouts and cut them in half lengthwise.
Toss the sprouts on the baking sheet with half of the olive oil and a pinch of sea salt, then roast for 20-25 minutes until tender and charred.
Season the chicken breast with garlic powder, sea salt, and black pepper.
Heat the remaining olive oil in a skillet over medium-high heat and sear the chicken for 5-7 minutes per side until fully cooked.
In a small saucepan, combine the balsamic vinegar and honey; simmer over medium-low heat for 3-5 minutes until it reduces into a thick glaze.
Place the walnuts in a dry pan over medium heat for 2-3 minutes, tossing frequently until fragrant and lightly toasted.
Slice the chicken and combine it with the roasted Brussels sprouts and walnuts in a large bowl.
Drizzle the balsamic glaze over the mixture and toss gently to coat everything evenly before serving.