In a large skillet over medium to medium-high heat, fry bacon until chewy-crisp. Remove from skillet to paper towel-lined plate to cool. Drain fat from skillet.
Return same skillet to medium to medium-high heat and add ground beef and onion. Cook until beef is browned and onion is tender. Drain fat.
Roughly chop the cooled bacon and add to skillet with beef and onion. Then add beans, yellow mustard, brown sugar, and black pepper. Fold to combine. Heat until warmed throughout. Serve hot.
