Prep the lamb leg by trimming away large areas of fat that may not render, remove as much silverskin as possible
Coat the entire leg with the dijon mustard, and then coat with the dry rub mixture. Score the meat diagonally and press dry rub mixture into the cuts
Cover the leg in plastic wrap and place in fridge for a couple of hours to overnight
Pre-heat a smoker to 225, place on smoker with probe inserted into the thickest portion. Don't place probe against bone. Cook for about 3.5 to 4 hours, until internal temp reaches 135. Baste or spritz with apple cider vinegar every hour.
When the internal reaches 135, turn smoker up to 400 (or use an oven) to crisp up the outside, until internal temp is 140.
Let rest for 30 minutes, carve
Serve with rosemary garnish and shallots (optional)