In a large pot, combine 5 cups of water with 1 tablespoon of kosher salt and bring to a rolling boil. Carefully add the halved Brussels sprouts and cook for 4 to 5 minutes.
Drain the sprouts immediately. Transfer them to a serving bowl and toss with 2 1/2 tablespoons of butter or olive oil. Season with freshly ground black pepper to taste. Serve while hot.