This is a commitment of time and money. The process is a bit macabre, so the more sensitive reader will want to skip this one. Also, take it easy on the younger and more gentle family members if doing this at home. Start 12 hours ahead of meal-time. If the lamb comes from the butcher, let it get to room temp for some 6 hours.
I have done this three times for Passover meals feeding 200, so I have made the mistakes and learned hard.
Unless you live here, you cannot imagine how windy Montana is — just about all the time or at any time. Therefore, an enclosed, professional-grade rotisserie is the only way to go for me. The wind blows the heat away from an open-air system — and could blow sparks into the dry grass (and get your name in the newspaper). The best rotisserie will have a “cage” that uses large wing nuts so that the lambs are held securely onto the rotisserie. I have no experience with wood or charcoal cooking.
Whatever your system, INDIRECT heat is required. Have a large, full tank of propane. Two small tanks is ideal. Do not turn the thing off after it has been going for several hours or you may not get it to re-light. The propane is evaporating from liquid to gas and the tank will become FREEZING cold and the regulator will be FREEZING cold and may become blocked for quite awhile if the flow stops. Switch tanks fast.
Procure a twenty to thirty pound lamb or two. 1 mature sheep will take forever to cook. Each will need about 10 pounds of leeks, plus 1/2 pound of fresh rosemary and 1/2 pound of fresh thyme, plus a quart of olive oil. Also 10 lemons each and 1/2 box of Kosher salt – coarse. Leeks look like big green onions, but they are mild in flavor and go well with lamb.
Last year, we got two young sheep (older lambs) from the pastor who raises sheep. Lamb is much different from mutton, so a big old ram is not going to please many of the gustatory critics who attend your event. Cast about and see if a farmer will give you a lamb or two as a donation (tax write-off) — a larger herd is not always desired.
Say good-bye to Fluffy. You can pay the butcher to do this for you — or you can do it the old-fashioned way. Using some means other than poison, kill the critter. And, yes, cut his little throat and hang him by the heels for an hour to bleed out. Sprinkle a bucket of cold ashes from the fireplace (or lye) on the blood — it freaks me out to see dogs licking blood! Better, dig a hole under the lamb to catch the blood and refill with dirt.
The Jews (even today), use the kosher method to exsanguinate all critters as painlessly as humanly possible, so the lamb bleeds to death and seems to fall asleep.
While hanging, skin and dress the carcass. Rinse and clean completely. Remove the head. Remove the lower limbs below the first joint off the shoulder (distal from the shoulder) at the hocks and “knees”. (Where are you gonna put these?)
Rub the entire lamb (within and without) with coarse Koshering salt. Run the spit through the pelvis and out through the neck. Fill the cavity with leeks, rosemary, thyme, and lemons – cut in half and squeezed just a bit. Some 10 pounds of leeks may be required.
To lace up the lambs, nothing works like new wire for an electric fence. Twine will burn. Use needle-nose pliers and cut a five foot strip of wire. Start at the neck and lace up the carcass. Keep the leeks in while doing this. The pliers will help you press the wire through the flesh and sew it up. Lash the extremities to the tabs of wire under the belly tightly or they will burn up. They will likely get over done anyway.
If you wrap lots of wire around the carcass to secure the limbs and all to the rotisserie, the wire will cut into the flesh as the lambs cook, so avoid this if possible.
Baste the exterior of the lamb with a mixture of olive oil, lemon juice, salt, and rosemary/thyme. Use a brush with a LONG handle. Start the heat rolling and get the temperature to 300.
IMPORTANT: stay with the lamb after cooking for four hours. When the fat gets liquefied, you could have a HUGE grease fire that may melt parts of the grill or set the house on fire. Not an issue at all when starting out, so run your errands then. After 4 hours, settle down by the grill, listen to some music and stay put.
Baste the lamb while it turns every hour. Opening the system will dump the heat, so more frequent opening becomes counter-productive.
The biggest variable is the size of the lamb. The last part to cook will be the pelvis area. Use a meat thermometer to measure the temperature there, staying just off the bone. Lamb can be served just like beef — rare is OK. The rest of the lamb will be over-done if you get the temperature to medium at the center of the pelvis, so this area will be under-cooked and likely need to be finished off in the oven, roaster, or large skillet. Or enjoy as medium rare.
Turn the heat down to its lowest setting and remove the lamb from the cooker. Take it off the rotisserie and place the lamb on a carving area. Break down the lamb with one sharp knife and one less sharp, heavy “boning knife”. Cut the pelvis last so the residual heat can cook it more.
Place all the leeks in a large bowl. Take each one and cut away the coarse green part and discard. Slice the remaining white part and soft green part like big green onions, with 1/2 inch slices to serve with the lamb. Make certain they are cooked completely — saute in a large skillet if need be. They will likely have enough oil and salt on them already. Serve on the side.