With the rack in the middle position, preheat the oven to 165 °C (325 °F).
On a work surface, open the roast flat, cut into large pieces and cut out most of the fat, as needed. Season with salt and pepper.
In a large ovenproof skillet, brown the meat on both sides in the oil. Deglaze the pan with the broth and Worcestershire sauce. Brush the meat with the mustard and place the garlic cloves around the meat, in the broth.
Cover and bake for about 2 hours and 30 minutes or until the meat is fork-tender. Serve with Colcannon or mashed potatoes.