Preheat oven to 425°F (220°C). Line a large, rimmed baking sheet with parchment paper or foil for easier cleanup.

In a large bowl, toss the trimmed Brussels sprouts with 3 tablespoons of olive oil, kosher salt, black pepper, and garlic powder until they are evenly coated.

Transfer the seasoned Brussels sprouts to the prepared baking sheet. Ensure they are spread out in a single layer, cut-side down. Note: Overcrowding the pan will cause the sprouts to steam rather than crisp.

Roast the Brussels sprouts for 15 minutes. Remove the pan from the oven and shake it gently to flip the sprouts. Return to the oven and roast for an additional 5 to 10 minutes, or until the sprouts are tender on the inside and deeply charred and crispy on the outside (total roasting time: 20–25 minutes).

While the Brussels sprouts are finishing cooking, prepare the glaze. In a small saucepan, combine the balsamic vinegar, honey (or maple syrup), and water (if using).

Heat the mixture over medium heat. Bring it to a gentle simmer, then reduce the heat to medium-low. Allow the mixture to gently bubble and reduce for 3 to 5 minutes, stirring occasionally, until it thickens slightly to a syrupy consistency. Remove from heat immediately. Do not over-reduce, as it will become too hard once cooled.

Remove the crispy Brussels sprouts from the oven and transfer them immediately to a large mixing bowl. Pour the warm honey balsamic glaze over the roasted sprouts.

Toss quickly but gently until all the sprouts are coated in the sticky glaze. Serve immediately while hot and crispy.