Prepare the joint

Cup of Yum
1. Allow the beef to come to room temperature for 30 minutes or up to an hour for a large joint.
2. Slice the fat on top of the joint on the diagonal to create a diamond pattern (unless already prepared). Season the beef library with several turns of the salt and pepper mill on all sides and sprinkle with dried thyme. Allow the beef to come to room temperature for 30 minutes or so.
3. Heat the oil in a large skillet and sear the beef over high heat on all sides, using tongs to turn it. Set aside.
4. Add the sliced onion to the hot pan and pan fry until colored. Set aside.
5. Deglaze the hot pan with a generous slug of red wine (or you can use Marsala) and cook for a couple of minutes until reduced. Use a wooden spoon to scrape any browned bits loose (all the yummy flavor hides in these!).
6. Pour the pan juices into the slow cooker. Add the onion, bay leaves and rosemary. Place the rib joint in the crock pot resting it on the bones with the skin side uppermost. Pour in the beef broth.
7. Cover and cook for approximately 3-3 ½ hours on LOW or until the desired temperature is reached on an instant read thermometer (see notes for a guide). Check the temperature after 3 hours or sooner if you use a smaller joint than the one specified.
8. Rest the beef for 20-30 minutes or longer, loosely covered with foil while you prepare the gravy.

Make the gravy

1. Strain the cooking liquid from the slow cooker into a saucepan. Stir in Worcestershire sauce, mustard and the xanthan gum (or cornstarch slurry). Bring to a simmer, cooking until the gravy thickens. Check the seasoning and adjust if needed.

Slice and serve

1. Remove any string from the joint. Position a sharp knife between the ribs and meat and slice pushing against the bones to release the meat from the ribs.
2. Slice the meat thinly across the grain and serve with the gravy and your choice of sides.