Preheat oven to 400F and line a baking sheet with aluminum foil for easier cleanup. Add the brussels sprouts to the baking sheet, evenly drizzle with olive oil, season with salt and pepper, and toss with your hands to evenly coat. Arrange the sprouts with the cut-side (flat side) down and bake for about 18 minutes, or until the tops of some of the sprouts are turning light brown. Remove baking sheet from oven, flip sprouts over with a tongs, and evenly drizzle with balsamic and evenly sprinkle with brown sugar. You only need to put a tiny pinch of sugar on the top of each sprout. It helps with caramelization and takes the edge off the intensity of the balsamic and doesn't make them taste sweet, but if you're adverse to adding sugar, it can be omitted. Return baking sheet to oven and bake for about 10 to 15 minutes, or until sprouts are as caramelized and browned as desired. Baking times will vary based on the size of the sprouts used, personal preference for doneness, oven and climate variances, etc. Keep a close eye on them in the last 10 minutes of baking because they can go from underdone to overdone and burnt in just a couple minutes. Optionally garnish with cheese or pistachios before serving. Brussels sprouts are best warm and fresh.