Cut the bacon into 1/2" pieces and cook it in a large skillet until the bacon fat is rendered and it is just starting to brown. Add the garlic and cook for one additional minute. Strain from the skillet into a food processor, leaving the fat in the skillet.
Chop the onions into quarters and put into the food processor with the bacon and garlic. Pulse the mixture until it resembles ground beef and still has some text but small pieces.
Put the ground beef into a medium size bowl and add the bacon/onion mixture, bread crumbs, cayenne pepper, parsley, egg, and salt. Mix thoroughly with your hands.
Form mixture into meatballs. I make larger meatballs so get about 18; but you can make them smaller, about 1 inch, and get 24 meatballs.
Heat the skillet over medium heat. Add additional oil if necessary to lightly cover the bottom. Brown the meatballs, turning every couple of minutes to brown all sides, should take 8-10 minutes. Remove from the pan and set aside.
Wipe any fat from the pan and add the barbecue sauce, water, molasses, brown sugar (start with 2 Tbsp and taste; add more if you want a bit sweeter), mustard, cumin, and bourbon to the pan, simmer until will combined and warm.
Add the meatballs to the sauce and let them simmer 10-15 minutes. Serve with toothpicks or small forks as an appetizer or over pasta noodles for a main course.
Garnish with parsley if desired.