Rinse 1 lb fresh Brussels sprouts under cold water, then pat completely dry — moisture steams instead of sears. Trim the woody stem end, then halve each sprout lengthwise through the core. The flat cut side is what makes contact with the skillet and builds that char. Cut larger sprouts smaller so everything is roughly the same thickness. Measure out oil, salt, pepper, and any finishing ingredients before the pan goes on the heat — the sear moves fast.

Heat a large cast iron or heavy skillet over medium to medium-high heat. Add 2 tbsp high-smoke-point oil (vegetable or avocado) and let the pan get fully hot. Arrange sprouts cut-side down in a single layer — no crowding. Cook in batches if needed. Leave undisturbed for 3–4 minutes until the cut side is deeply golden to dark brown. Stir or toss to expose rounded sides. Season with salt, pepper, and garlic powder. Cook another 5–6 minutes, stirring occasionally, until tender when pierced. Total time per batch: 8–10 minutes. If cooking in batches, transfer first batch to a plate, add fresh oil, and repeat. Return all sprouts to the pan. Add 1 tbsp butter and 1 tbsp balsamic vinegar. Toss and cook 1 more minute until butter melts, vinegar reduces slightly, and sprouts are coated.

Look for a deeply browned to nearly blackened flat face with a tender interior — easily pierced with a fork. Crispy, dark outer leaves are a good sign. If sprouts still feel firm or squeaky after full cook time, give them 1–2 more minutes with occasional stirring. Serve immediately — char and caramelization fade as they sit. Two mistakes to avoid: (1) Overcrowding the pan causes steaming instead of searing — cook in batches if needed. (2) Moving sprouts too soon prevents a proper crust from forming on the cut side — let them sit undisturbed.