If there is more than 1 Tbsp of bacon fat in the pan, carefully drain excess fat off (keeping bacon in the pan) until you have about 1 Tbsp of fat left in pan. Add raw Brussels to the pan and toss to coat. Stir fry the brussels with the bacon about 2 minutes, stirring occasionally.
Transfer the pan to the oven and bake, stirring twice throughout, until bacon is crispy and Brussels are very brown and crispy, about 25 minutes. Remove from oven, and sprinkle with small amount of salt (be careful as bacon is salty already)and pepper, then drizzle with balsamic glaze or balsamic vinegar.