Place the brussels sprouts in a large bowl and cover with warm tap water. Allow to sit for 10 minutes.
Drain the sprouts and lightly pat dry with a paper towel. Dry out the bowl the sprouts were soaking in and return the dry sprouts to the bowl.
Drizzle the brussels sprouts with the olive oil and season with salt and pepper to taste. Toss to coat.
Cook the brussels sprouts in the air fryer for 5 mins at 400 degrees. Pull out the trays and flip the sprouts over. Cook an additional 5 minutes, or until the sprouts are crispy and just tender enough to stab with a fork.
While the brussels sprouts are air frying, warm the butter in a small saucepan over medium high heat. Cook until the butter begins to bubble and begins to turn brown. Remove the butter from the heat and stir in the soy sauce and balsamic vinegar.
Transfer the brussel sprouts to the butter sauce and toss to coat. Place the sprouts in a serving dish and sprinkle with crispy bacon.