Use a mortar and pestle to pound cilantro stems and roots, ginger, garlic, and shallots, to a paste, pounding each ingredient thoroughly before adding the next. Then add the fish sauce to create a thin paste. You'll probably need to work in batches. Transfer to a large bowl and stir in the coconut milk. Grind the dried chilies and peppercorns together in a spice grinder. Add the lime zest and kaffir leaf pieces, and grind them all together until the mixture is fine and slightly moist. Stir the spice mixture into the coconut milk mixture. Rub the pig down and up (put it in a giant garbage bag or large plastic bin), inside and out with the kosher salt. Then rub the coconut mixture all over the salted pig, inside and out. Put the pig, belly up, in a large heavy-duty trash bag and pour any remaining marinade inside the cavity. Squeeze out as much air as possible from the bag and tie it. Let sit for 2 to 3 days in a large refrigerator.
Get a large smoker up to 200 degrees F. Remove the pig from the bag, saving as much of the marinade as possible. Put the pig in the smoker, belly up, and pour the marinade into the belly cavity. While it's cooking, focus on stoking your fire, maintaining the temperature, and drinking. The piggy is ready when the internal temperature of the thickest part of the shoulder is at 170 degrees F. Any pig over 140 pounds or so will take the full 24 hours. If you're working with 50-pounders, though, it'll take closer to 12 hours.
Remove the pig from the smoker and transfer it to a large table covered with a plastic tablecloth or tarp. Let it rest for about 20 minutes, but pork-mad people will undoubtedly start ripping into the fatty flesh before you can get it to the table. I know because I'm one of them. Use a heavy-duty, sharp knife to remove the primals, peel the skin, and chop the meat. Be sure to have a catch basin for the juice and fat that will be spilling out from the smoky carcass. Toss the reserved cilantro leaves over the chopped meat.
Excerpted with permission from Eat With Your Hands by Zak Pelaccio (Ecco, 2012)