Preheat your oven to 375 degrees F (190 degrees C). In a large (10-12 inch) cast iron skillet, cook the bacon at medium heat until just beginning to get crispy, about 5-8 minutes. Add the butter, finely minced shallots, and cut brussel sprouts. Continue to cook at medium heat for an additional 5 minutes, or until the brussel sprouts are seared.
In a small bowl, combine the brown sugar, Dijon mustard, Balsamic vinegar, paprika, ground mustard, and crushed red pepper flakes. Add the Dijon sauce to the cooked brussel sprouts in the cast iron skillet, and stir to coat all of the brussel sprouts thoroughly.
Transfer the cast iron skillet and contents to the oven and allow to cook at 375 degrees F (190 degrees C) for 45 minutes, or until tender when forked. Stir the contents of the skillet at about 25 minutes into cooking, if desired (as I did) to help cook thoroughly and keep the coating even and moist. Remove from the oven when done and serve immediately.
*If you don't have a cast iron skillet for these brussel sprouts, pan sear them in a skillet or frying pan and then transfer to a baking dish.