Preheat your oven to 400 degrees F. Line a large rimmed baking sheet with parchment paper or foil and set it aside.

Trim the stem end off each Brussels sprout and pull away any yellowed outer leaves. Cut each sprout in half straight through the stem so both halves stay intact. Add them to a large mixing bowl.

Drizzle the olive oil and balsamic vinegar over the sprouts. Sprinkle with salt, pepper, and garlic powder if using. Toss everything together until each sprout is evenly coated.

Spread the sprouts out on the prepared baking sheet in a single layer, cut-side down. This is the most important step for caramelization, so resist crowding the pan. If they are too tight, use two baking sheets.

Scatter the bacon pieces evenly over the top of the sprouts. The bacon fat will drip down and baste the sprouts as everything roasts.

Roast at 400 degrees F for 22 to 25 minutes. Do not flip or stir them. The cut sides should be deep golden brown and a little sticky when done. The bacon should be fully crisp. Check at 22 minutes and give them the full 25 if the cut sides still look pale.

Transfer to a serving platter and taste for salt. Serve immediately while the edges are still crisp.