Trim and Score: Trim away loose fat or silver skin. Use a sharp knife to score the fat cap in a 1-inch crosshatch pattern, cutting just down to the meat.
Inject the Meat: Whisk the injection ingredients until the sugar and salt are dissolved. Inject the liquid into the Boston Butt in a grid pattern every inch.
Apply Binder and Rub: Slather the entire butt with a light coat of yellow mustard. Generously apply the BBQ rub to all sides, ensuring it gets into the crosshatch scores.
Prepare the Big Green Egg: Set up your Big Green Egg for indirect cooking with the ConvEGGtor (legs up). Add Hickory or Oak wood chunks. Stabilize the temperature at 350°F.
The Clean Smoke: Wait for the "billowy" white smoke to turn into a thin, translucent blue. This signals the Egg is ready.
The Cook (Phase 1): Place the pork on the grate fat side down to protect the meat from the heat source. Close the dome.
The Spritz: Every hour, mist the pork with the Apple Juice/Vinegar mix to maintain moisture and build the bark.
The Wrap: When the internal temperature reaches 165°F (usually around the 3-hour mark), remove the pork. Place it on a double layer of foil, add 1/4 cup apple juice, and wrap tightly.
The Cook (Phase 2): Return the wrapped pork to the Egg (fat side down). Continue cooking for approximately 2 more hours until the internal temperature reaches 195°F–203°F.
The Butter Test: The pork is done when your temperature probe slides in and out of the meat with no resistance, like softened butter.
The Rest: Remove the pork from the Egg and let it rest, still wrapped, for at least 1 hour (In a cooler wrapped with towels for up to 4 hours).
Pull and Serve: Remove the bone (it should slide out clean!). Chop or shred the meat, mixing in the crispy bark from the fat cap. Serve on toasted buns.