Place cast iron skillet in the oven on lower rack. Preheat oven and cast-iron skillet to 400 F.
Cut the ends off the brussel sprouts, then cut each brussel sprout in half the long way.
Add the brussel sprouts into a medium bowl. Drizzle some extra virgin olive oil over them. Sprinkle with some salt and pepper to taste and give them a quick mix. Make sure that every piece of brussel sprout is coated with oil.
Place the brussel sprouts onto the preheated cast iron skillet. Arrange them so that each brussel sprout half is touching the hot cast-iron pan.
Place into the oven on lower rack and bake for 30 minutes.
Remove from oven. Drizzle with about a couple teaspoons of extra virgin olive oil. Serve as a side dish with roasted turkey, chicken, steak, or anything you can imagine.