In the bowl of a small food processor, add the first six ingredients. Pulse just until the mixture comes together and the garlic is minced. Do not over process. You do not want a paste.

To the bowl of the Instant Pot (or slow cooker), add the beef broth and wine. Place the mushrooms inside and lay the roast on top of the mushrooms.

Spread the spice mixture onto the top of the roast.

Close the lid and seal the vent. Cook on high pressure for 1 hour. Let the steam naturally release for 15 minutes before manually venting. Press cancel when done. If using a slow cooker, cook on low for 8 hours.

Remove the roast from the pot and set on a large cutting board or plate. Use a slotted spoon to remove the mushrooms from the pot and reserve them on a platter. Use two forks to shred the roast.

Strain the remaining juices through a fine sieve. Return the broth to the pot (or a sauce pan). Use the sauté function to bring the broth to a boil. Once a boil is reached, add the xanthan gum and whisk continuously until a thick gravy consistency is reached. Press cancel and transfer the gravy to a gravy boat.

Serve the roast with the mushrooms and gravy. Garnish with fresh rosemary, if desired.