Trim the stems of the sprouts and cut them in half from top to bottom.
Brush the oil evenly over the bottom of a large, oven-proof skillet. Arrange the brussels sprouts, cut side down, in the skillet.
Place the skillet over medium-high heat and sprinkle the tops of the Brussels Sprouts with the sugar and salt. When the pan is hot, put 2 tablespoons of butter in the pan.
Once the butter is melted place the pan in the hot oven. Roast for 10-12 minutes until the sprouts are caramelized.
Remove the skillet from the oven and add the vinegar and the last tablespoon of the butter. Toss them around to deglaze the pan and coat the sprouts.