Preheat the oven to 300°. Pat the beef dry and coat it with salt and pepper.
Heat the oil over high heat in a large skillet. Brown the ribs on all sides, about 15 minutes total. Remove from the pan and set aside.
Reduce the heat to medium and add the onion, celery, carrot, garlic, thyme, parsley, and peppercorns. Cook the vegetables until caramelized, about 15 minutes. Add the tomato paste and cook another 5 minutes.
Whisk together the beef stock and cornstarch until combined. Add the beef back to the pan along with the beef stock and beer, and simmer until reduced by one-third. Cover the pan with foil or lid, and braise in the oven until fork tender, about 2 hours.
Remove the lid and cook for another 20 minutes. Remove the beef. Strain the sauce, return it to the pan, and reduce by one-quarter. After the meat has cooled enough to handle, pull it apart, removing the large chunks of fat, but leaving a few for flavor and texture.