Preheat the oven to 400ºF with the oven rack in the center position.

Over medium heat-high, heat olive oil in a large cast-iron or other oven-safe skillet. Add Brussels sprouts and season with salt and pepper to taste. Cook, stirring occasionally, until the sprouts start to turn a brown.

Once browned, put the skillet into the oven and roast for 15-20 minutes, stirring halfway through. They are done when they are tender and are a rich brown color.

While your sprouts are roasting, add maple syrup and balsamic vinegar to a small skillet. Heat over medium-high, bringing to a boil while stirring constantly. Once it reaches boiling, reduce the heat to medium. Continue stirring until the vinegar mixture reduces to about 1/3 its original volume. It should be thick and syrupy. Be careful not to overcook it or it will become hard and sticky.

Transfer the Brussel sprouts to a plate and drizzle with the balsamic glaze. If desired, you can season with more salt and pepper.