Set up your smoker for indirect cooking at 250°F
If you bought a large leg of lamb, it should have three distinctive parts: a piece of the hip, top of femur and thigh, and the knee and lower leg. Trim off the shoulder part, so it’s just the leg. Don’t throw away your trimmings, you can always use it for lamb sausage!
Trim any loose hanging fat. Don’t trim the fat cap—during the low slow cooking, it will render, adding flavor to the lamb.
Instead of doing a complete Frenching of the leg at the start, you will do a quick prep so you can French it after cooking. Since it's for presentation, doing it beforehand keeps the bone nice and white for presentation, otherwise, the smoke will darken it.Make a deep cut into the meat. During the cooking process, this thin piece of meat will dry out, and making a deep cut into the meat will make it easier to remove after its cooked. Cut down to the bone. Score the fat cap in a diamond pattern to expose the meat (do not cut through the meat completely!). This helps to render the fat, and will allow the herbs and spices to penetrate to the meat.
Make a few small slits into the meat along your scoring pattern. These slits will become small flavor pockets when you add herbs and garlic into them (in a few steps - patience!)
Slice each garlic clove in half. This will help to release some of the oils and improve the flavor.
Peel the ginger and slice thinly. Chop the rosemary into 1 ½ to 2-inch pieces.
Cover the underside of the lamb completely with the mustard. Season generously with the SPG seasoning.
Turn the leg of lamb over, so that the scored side faces upwards. Apply the mustard into the meat. Season generously with the SPG seasoning. Stuff the garlic and ginger into the slits you made earlier. Do the same with the rosemary.
Place the leg of lamb on the grill and insert a temperature probe into the thickest part of the meat. Close the lid and get your smoke started.
Spritz every hour with your ACV/Juice spritz solution, double-checking the temp each time with your handheld thermometer.
Once you reach your target temperature (135°F for Medium Rare), remove the leg of lamb from the smoker and let it rest tented in foil for at least 20 minutes. If you let it rest longer, wrap in a towel and place it in a closed cooler to keep the temperature from falling too far.
Remove the "frenched" meat from the bottom of the leg - it's now so overcooked that it should come right off in your hand.
Slice and Serve!