Preheat your oven to 400°F and line a large baking sheet with parchment paper.
Trim the ends off the Brussels sprouts and slice them in half vertically.
In a bowl, toss the sprouts with half of the olive oil, sea salt, black pepper, and garlic powder.
Spread the sprouts on the baking sheet and roast for 20-25 minutes until the outer leaves are crispy and charred.
While the sprouts roast, season the chicken breast with the remaining salt and pepper.
Heat the remaining olive oil in a skillet over medium heat and sear the chicken for 6 minutes per side until golden and cooked through.
Add the walnuts to the baking sheet during the last 3 minutes of roasting to bring out their nutty aroma.
Transfer the roasted sprouts and walnuts to a bowl, drizzle with balsamic glaze, and toss before serving with the sliced chicken.