Cut off the root ends of the brussels sprouts and pull off any old outer leaves. Slice them in half.
In a large skillet, render the fat from the bacon over low to medium-low heat. Once the fat has mostly melted down, turn up the heat and brown until caramelized and crunchy. Set aside to drain on a paper towel. Remove all but two tablespoons of the bacon fat from the pan.
In the same skillet, add the brussels and allow them to caramelize on one side. Deglaze the pan with the balsamic vinegar, using a spatula to scrape up any brown bits and incorporate them with the brussels. Continue to saute the brussels on high heat for a few minutes, shaking the pan, until they have softened up a bit. Add the bacon back to the pan along with 2 tablespoons of the brown sugar. Stir until the sugar has completely dissolved and is evenly coating the brussels sprouts.
Taste; add the remaining brown sugar if desired, allowing it to dissolve before removing the pan from the heat. Add kosher salt and ground black pepper to taste. (Note: you might not need any salt because of the bacon).