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 and toss with 0.5 tablespoons of olive oil, half of the sea salt, and half of the black pepper.
Spread the sprouts in a single layer and roast for 20-25 minutes, tossing halfway through, until the outer leaves are charred and the centers are tender.
While the sprouts roast, season the chicken breast evenly with garlic powder and the remaining sea salt and black pepper.
Heat the remaining 0.5 tablespoons of olive oil in a medium skillet over medium-high heat.
Add the chicken to the skillet and sear for 6-7 minutes per side, or until the internal temperature reaches 165°F.
Remove the chicken from the heat and let it rest for 5 minutes before slicing into thin strips.
In a large mixing bowl, combine the roasted Brussels sprouts and sliced chicken.
Drizzle with the balsamic glaze and toss gently to coat.
Roughly chop the walnuts and sprinkle them over the top before serving warm.