Preheat your oven to 400°F and line a large baking sheet with parchment paper.
Trim the ends off the Brussels sprouts and cut them in half lengthwise.
Toss the sprouts on the baking sheet with half of the olive oil, sea salt, and black pepper.
Roast the Brussels sprouts for 20 to 25 minutes, tossing halfway through, until they are tender and the edges are charred.
While the sprouts roast, heat the remaining olive oil in a skillet over medium-high heat.
Season the chicken breast with a pinch of salt and pepper, then sear for 6 to 7 minutes per side until the internal temperature reaches 165°F.
During the last 3 minutes of roasting the sprouts, add the walnuts to the baking sheet to lightly toast them.
Mince the garlic and add it to the skillet with the chicken for the final 60 seconds of cooking.
Slice the cooked chicken into strips.
In a large bowl, combine the roasted sprouts, toasted walnuts, and sliced chicken.
Drizzle the balsamic glaze over the mixture and toss gently to coat before serving.