Add the onion, carrot, and another pinch of salt to the pan and sauté for 5 minutes, until soft. Add in the garlic and cook for another 3 minutes. Add in the tomato paste and peppercorns and cook for 1 minute. Add the beef back in, along with any juices that have accumulated, along with the broth Guinness, Worcestershire sauce, and thyme. Bring to a boil, then cover and put in the oven for 45 minutes. Remove the cover and cook for another 45 minutes.