Preheat your oven to 425°F (220°C). Line a large, rimmed baking sheet with parchment paper or foil for easier cleanup. This high heat is key to achieving a crispy texture.

In a large bowl, combine the trimmed Brussels sprouts with the olive oil, kosher salt, black pepper, and garlic powder. Toss vigorously until all sprouts are evenly coated.

Transfer the seasoned Brussels sprouts to the prepared baking sheet. Ensure they are spread out in a single layer with the cut side down. Avoid overcrowding the pan; if necessary, use two sheets to ensure they crisp up instead of steam.

Roast for the initial 15 minutes. Remove the pan from the oven, gently shake the pan or use a spatula to flip the sprouts, and return to the oven for an additional 5 to 10 minutes, or until deeply charred and tender.

While the sprouts are finishing the second roast, 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 to a gentle simmer, then immediately reduce the heat to medium-low. Allow the mixture to bubble and reduce for 3 to 5 minutes, stirring occasionally, until it has thickened slightly to a light syrupy consistency. Remove from heat immediately.

Remove the crispy Brussels sprouts from the oven. Immediately transfer the hot sprouts to a large mixing bowl. Pour the warm honey balsamic glaze over the roasted vegetables.

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