Preheat your oven to 400°F and line a baking sheet with parchment paper.
Trim and halve the Brussels sprouts, then toss them on the baking sheet with 0.5 tablespoon of olive oil, garlic powder, and half of the sea salt and black pepper.
Roast the Brussels sprouts for 20-25 minutes, tossing halfway through, until the edges are crispy and caramelized.
While the sprouts roast, season the chicken breast with the remaining sea salt and black pepper.
Heat the remaining 0.5 tablespoon of olive oil in a skillet over medium-high heat and sear the chicken for 6-7 minutes per side until fully cooked.
Add the chopped walnuts to a small dry pan over medium heat for 2-3 minutes, stirring constantly until they are fragrant and toasted.
Slice the cooked chicken into strips and combine it with the roasted Brussels sprouts.
Drizzle the entire dish with the balsamic glaze and garnish with the toasted walnuts before serving.