In a large cast iron skillet, cook the chopped bacon over medium high heat until crispy, stirring regularly (about 5 minutes). Remove the bacon from the skillet and set aside. Leave the bacon grease in the skillet (about 1 to 2 tablespoons of grease).
Place the sliced Brussels sprouts in the skillet. Cover and cook over medium heat for two minutes, stirring every 30 seconds or so. Add the bacon bits and balsamic vinegar. Stir the mixture and cook for another two minutes over medium low heat, stirring constantly, until the sprouts are crisp-tender and still bright green.
Season with salt and pepper to taste, and serve immediately.