Preheat oven to 425 degrees
Fill a large bowl with cold water and quickly dunk the brussels sprouts into them to get off any surface dirt.
Dump them out onto a clean tea towel and dry them off, or put them in your salad spinner and take them for a ride (they will caramelize better if they are dry)
Cut the tough stems off, and then bisect them each in half. Some of the outer leaves will fall off. Place them to the side, and return the halved brussels sprouts to the cleaned and dried bowl.
Drizzle the sprouts with 1 1/2 tablespoons of olive oil and season well with the salt and pepper. Toss well to coat.
Place the brussels sprouts in a single layer on a baking tray (flat side down)
Bake in preheated oven for 10 minutes. While they are baking, put the leftover leaves in the bowl, and toss them to coat in the leftover oil, salt and pepper.
After 10 minutes, take the pan out and give it a good shake. Add the remaining leaves and bake for another 10 minutes until golden brown and caramelized.
Slide the roasted brussels sprouts back into the bowl and pour over the balsamic reduction. Toss well to coat, taste for seasoning and adjust, then serve.