Preheat your oven to 400°F (200°C) and line a large baking sheet with parchment paper.
Trim the ends of the Brussels sprouts and slice them in half vertically.
Place the sprouts on the baking sheet, drizzle with half of the olive oil, and season with half of the sea salt and black pepper.
Roast the Brussels sprouts for 20-25 minutes, tossing halfway through, until the outer leaves are charred and the centers are tender.
While the sprouts roast, cut the chicken breast into bite-sized pieces and season with garlic powder and the remaining salt and pepper.
Heat the remaining olive oil in a skillet over medium-high heat and sear the chicken until golden brown and cooked through, about 6-8 minutes.
In a small dry pan, toast the chopped walnuts over medium heat for 2-3 minutes until they become fragrant and slightly darkened.
In a large mixing bowl, combine the roasted sprouts, seared chicken, and toasted walnuts.
Drizzle the balsamic glaze over the mixture and toss thoroughly to ensure every piece is coated before serving.