Combine the brown sugar, balsamic vinegar, and mustard in a medium size mixing bowl. Stir to combine.
Cut the bacon into bite size pieces and place in a plastic baggy or sealable container.
Pour just enough marinade over the bacon to cover it. You want to have at least half of the marinade left for the brussels sprouts. Place the bacon in the refrigerator for at least 4 hours and up to 24 hours. Cover the remaining marinade/glaze and refrigerate until use.
Cut the stems off of the washed Brussels sprouts and peel off any outer leaves that are dry or browning.
Put one cup of water into the inner pot. Put the Brussels Sprouts into the Air fry basket and put the pressure lid on. Turn the valve to seal and set on high pressure for zero minutes. *See note section for more information. When the display reads "done", immediately release the pressure.
Remove the basket with the Brussels Sprouts from the inner pot and set aside. Dump the water from the inner pot.
Turn the sear/sauté on high. Add the bacon and the marinade that is in with the bacon to the inner pot. Sauté on high and stir frequently until the bacon is almost cooked and the marinade has reduced. This takes about 5 minutes or so.
Remove the bacon and any liquid left from the inner pot and place in a small bowl. Rinse the pot. Preheat the Ninja Foodi on broil for 5-10 minutes.
Place the basket of Brussels sprouts into the inner pot and dump in the cooked bacon. Toss to distribute the bacon. Drizzle about 1-2 Tablespoons of the reserved glaze on top and broil for 5 minutes. Toss, add more glaze, and broil another 2-3 minutes. Repeat with adding glaze and broiling 2-3 minutes until the Brussels Sprouts are nice and brown, covered with the glaze, and are your desired texture. This usually takes 12-17 minutes.
Some food, including the Brussels sprouts in this recipe will cook to the desired doneness in the time it takes for the pot to come up to pressure. So, when a recipe calls for zero minutes of pressure cooking time, you hit the down arrows until the display reads 00:00 and hit start. The pot will build pressure and cook the food during this time, then it will immediately say done and revert to the Keep Warm function. With this recipe, you immediately release the pressure.