Preheat your oven to 400°F and line a baking sheet with parchment paper.
Trim the ends off the Brussels sprouts and slice them in half vertically.
Toss the sprouts with 1 teaspoon of olive oil, half of the sea salt, and half of the black pepper on the prepared baking sheet.
Roast the Brussels sprouts for 20 to 25 minutes, flipping halfway through, until they are tender and the edges are caramelized.
While the sprouts roast, season the chicken breast with garlic powder and the remaining salt and pepper.
Heat the remaining 1 teaspoon of olive oil in a skillet over medium heat and cook the chicken for 6 to 7 minutes per side until the internal temperature reaches 165°F.
In a small bowl, whisk together the balsamic vinegar and maple syrup to create the glaze.
In a small dry pan over medium-low heat, toast the walnuts for 2 to 3 minutes until fragrant, then roughly chop them.
Slice the cooked chicken and combine it with the roasted sprouts in a bowl.
Drizzle the balsamic glaze over the chicken and sprouts, toss gently to coat, and garnish with the toasted walnuts.