Preheat oven to 400°F. Put the bag of brussels sprouts into the microwave for 4 minutes with a couple of holes poked in the bag.
Saute bacon in cast iron pan then pull the pieces out of the pan.
Place brussels sprouts in a cast-iron frying pan (or a roasting pan, but a cast-iron frying pan will work great for this recipe). Toss in the garlic.
Toss with bacon grease so that the sprouts are well coated. Sprinkle generously with salt (at least a half teaspoon) and a few turns of black pepper.
Put brussels sprouts in the oven on the top rack, cook for 10 minutes, then stir so that the sprouts get coated with the oil in the pan. Cook for another 10 minutes.
Sprinkle with cooked bacon bits & balsamic vinegar