Preheat the Oven & Prep Pan: Adjust the oven rack to the middle position and preheat the oven to 400°F (200°C). Line a large, sturdy baking sheet with parchment paper for easier cleanup.

Prep Sprouts: Trim the dry, woody end off of each Brussels sprout and remove any loose outer leaves. Cut all of the sprouts in half lengthwise, ensuring a flat side is created on each half.

Seasoning: In a large mixing bowl, combine the halved Brussels sprouts with the 3 tablespoons of olive oil. Sprinkle the garlic powder, kosher salt, and black pepper over the oil-coated sprouts. Toss vigorously until all sprouts are evenly coated.

First Roast: Pour the seasoned sprouts onto the prepared baking sheet. Spread them out into a single layer, ensuring that the cut sides are facing down. Roast for 15 to 18 minutes, or until the edges are starting to brown and the sprouts are fork-tender.

Prepare the Glaze: While the sprouts are roasting, whisk together the brown sugar and balsamic vinegar in a small bowl until the sugar is dissolved and the mixture forms a sticky syrup.

Apply Glaze: Carefully remove the baking sheet from the oven. Drizzle the balsamic brown sugar glaze evenly over the roasted Brussels sprouts. Using a spatula, gently toss the sprouts right on the baking sheet to coat them completely with the glaze.

Final Caramelization: Return the baking sheet to the oven for an additional 5 to 7 minutes. Watch carefully during this final step; the glaze should thicken and caramelize slightly, becoming very glossy but not burnt.

Serve: Remove the sprouts from the oven immediately. Serve hot and fresh, scraping any remaining sticky caramelized glaze from the pan and drizzling it over the finished dish.