In a large skillet over medium heat, cook the bacon pieces until crisp and the fat has rendered, about 6–10 minutes. Transfer bacon to a paper towel-lined plate, leaving the drippings in the pan.

Increase heat to medium-high and add the Brussels sprouts cut-side down in a single layer. If the pan looks dry, add up to 1 tbsp olive oil. Season with kosher salt and black pepper.

Cook undisturbed until the cut sides are deeply browned, about 4–6 minutes. Toss and continue cooking, stirring occasionally, until sprouts are tender-crisp, about 6–8 minutes more. If they need help softening, add a splash of water and cover for 1–2 minutes.

If using garlic, add it in the last 30–60 seconds and cook just until fragrant.

Return the cooked bacon to the pan and toss to combine. Remove from heat and finish with balsamic vinegar (and optional Dijon mustard and/or maple syrup). Taste and adjust salt and pepper before serving.

Serve hot as a side. Tip: For extra crisp edges, avoid overcrowding the pan—cook in batches if needed.