Heat a large saute pan over medium-high heat. Add the bacon and cook until crisp, about 10 minutes. Remove the bacon from the pan with a slotted spoon and transfer to a paper towel lined plate. Set aside. Reduce the heat to medium-low.

To the same pan, add the onions, 2 tablespoons of butter and brown sugar. Season with salt and black pepper. Cook, stirring occasionally for 20-25 minutes or until the onions are brown and caramelized. Remove the onions from the pan with a slotted spoon and transfer to a separate bowl. Set aside.

Add the remaining 1 tablespoon of butter to the pan and add the brussels sprouts. Increase the heat to medium-high and cook until tender, about 7-8 minutes, stirring occasionally. Once tender, add the bacon and onions back to pan and toss the ingredients together.

Season with salt and pepper if necessary and serve immediately. Enjoy!