Preheat your oven to 400°F and line a large rimmed sheet pan with parchment paper for easy cleanup.
Trim the woody ends off the Brussels sprouts and slice them in half, then cut the chicken breast into uniform 1-inch bite-sized pieces.
In a small mixing bowl, whisk together the extra virgin olive oil, balsamic vinegar, honey, minced garlic, sea salt, black pepper, and dried thyme until well combined.
Place the chicken pieces and halved Brussels sprouts onto the prepared sheet pan and pour the balsamic dressing over the top.
Toss the ingredients thoroughly with your hands or tongs to ensure every piece is well coated, then spread them out into a single layer so they roast rather than steam.
Roast in the center of the oven for 20 to 25 minutes, tossing halfway through, until the chicken is cooked through and the Brussels sprouts are tender with beautifully charred, caramelized edges.