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.
Toss the halved sprouts with 0.5 tbsp of olive oil, half the sea salt, and half the black pepper on the baking sheet.
Roast the Brussels sprouts for 20-25 minutes, tossing halfway through, until they are tender and the edges are golden and crisp.
While the sprouts roast, season the chicken breast with garlic powder and the remaining sea salt and black pepper.
Heat the remaining 0.5 tbsp of olive oil in a skillet over medium-high heat and sear the chicken for 6-7 minutes per side until the internal temperature reaches 165°F.
During the last 2 minutes of the chicken cooking, add the chopped walnuts to the skillet to lightly toast them until fragrant.
In a small bowl, whisk together the balsamic vinegar and honey to create the glaze.
Remove the chicken from the pan and let it rest for 3 minutes before slicing into strips.
In a large bowl, combine the roasted Brussels sprouts, sliced chicken, and toasted walnuts, then drizzle with the balsamic glaze and toss to coat evenly.