Preheat your oven to 400°F (200°C) and line a large baking sheet with parchment paper.
Trim the woody ends off the Brussels sprouts and slice them in half lengthwise.
Place the sprouts on the baking sheet and toss with olive oil, sea salt, black pepper, and garlic powder until evenly coated.
Roast the sprouts 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 and pan-sear in a non-stick skillet over medium-high heat for 6-7 minutes per side until the internal temperature reaches 165°F.
Remove the chicken from the pan to rest for 5 minutes, then add the prosciutto slices to the same hot pan for 1-2 minutes until they become crispy.
Slice the rested chicken into thin strips and roughly chop the crispy prosciutto.
In a large bowl, combine the roasted Brussels sprouts, sliced chicken, and prosciutto, then drizzle with the balsamic vinegar and toss gently before serving.