Sear the beef in a hot pan, then brush again with mustard
Tuck a sprig of rosemary under the string and place the beef on a trivet of bone marrow
Add the chopped carrots, celery, onions, and garlic bulb, seasoned with salt, pepper, and olive oil
Roast at 220°C fan (428°F) for 20 minutes, then reduce to 160°C (320°F) and cook for 60 minutes for medium-rare (internal temperature 55°C/131°F)
Baste the beef with its own juices before removing from the oven
Rest the beef for 20 minutes before carving
Parboil the potatoes for 10 minutes
Melt beef dripping in the oven
Toss the potatoes in the melted beef dripping and season with smoked sea salt
Roast the potatoes for 1 hour, turning regularly for extra crispiness
Smash the roasted vegetables and remove the marrow from the bones
Place the tray over medium heat, deglaze with red wine, then add 1 cup of water mixed with 1 tsp corn starch
Cook the gravy, then strain through a sieve, adding the resting juices from the beef
