Cook the bacon in a saute pan over medium high heat for 4 minutes per side or until brown. Remove to a paper towel lined plate.

Remove all but 1 tablespoon of bacon grease from the pan (reserve the extra). Lower the heat to medium and add the onions and sugar. Cook for 15 minutes, stirring every 1-2 minutes, until the onions have caramelized. Remove to a plate.

Add 1 tablespoon of bacon grease to the skillet and add the Brussels Sprouts. Cook over medium high heat, stirring frequently, for 7-8 minutes or until they are cooked and beginning to caramelize.

Return the bacon and onions to the pan and add the butter, salt, and pepper. Cook for 1-2 minutes or until everything is heated through.