It's hard to do short ribs wrong, but this recipe does them oh-so right. The short ribs are braised in a chocolatey-Guinness beer liquid to give them a uniquely rich flavor.
Preheat the oven 350 degrees. Generously salt and pepper the short ribs. In a large heavy pot heat the oil until very hot. Sear the ribs until brown on all sides. Remove the ribs from the pan, and pour off the excess oil, but don't clean the pan.
Add the bacon and cook until the fat is rendered, about 5 minutes. Add the onions and cook until lightly browned, about 6 minutes. Don't worry if the onions start to fall apart, they will. Add the tomato paste and cook, stirring, for another 2 minutes. Add the beer, vinegar, beef stock, chocolate, and the ribs. Bring the liquid to a boil. At this point you can cover the pot and cook in the oven until they're fork tender, about 2 hours and 15 minutes.
Alternatively, just dump everything into the pot of a slow cooker, cover, and cook on low while you're at work. When you're ready to serve, remove the ribs, and onions from the pot, and pour the remaining liquid into a wide saucepan. Bring the liquid to a boil and cook until it's reduced by at least 1/3 (your call as to how thick you want the sauce). Taste and check for seasoning. Add the ribs and onions back to the sauce, serve with mashed potatoes and enjoy.