Start the desalting soak the night before or at minimum 4 hours before you plan to cook. Remove the corned beef from its packaging, discard the brine liquid, and rinse the brisket flat thoroughly under cold running water. Place it in a large container or pot, cover completely with cold fresh water, and refrigerate. Change the water once halfway through the soak. This step draws out excess salt from the cure so your finished product is flavorful but not punishingly salty. When you are ready to cook, remove the brisket, pat it completely dry with paper towels, and set it on a wire rack for 30 minutes to air-dry slightly at room temperature.

Fire up your smoker and dial it in to a steady 225 degrees Fahrenheit before you do anything else with the meat. For fuel, use a hardwood charcoal base and add 2 to 3 fist-sized chunks of cherry or applewood directly onto the lit coals. These fruit woods produce a mild, slightly sweet smoke that complements the savory brine without bulldozing the natural flavor of the beef. If you are using a pellet grill, load it with apple or cherry pellets and set it to 225 degrees Fahrenheit. Give the smoker a full 20 to 30 minutes to stabilize before you open the cooking chamber.

While the smoker comes up to temp, build your rub. In a small bowl combine the coarse black pepper, ground coriander, garlic powder, smoked paprika, onion powder, and cayenne if using. Mix well. Coat the entire surface of the dried brisket flat with a thin even layer of yellow mustard using your hands or a brush. The mustard acts as a binder and will cook off completely during the smoke, leaving no mustard flavor behind. Pat the spice rub generously over all surfaces of the brisket, pressing it firmly into the mustard layer to create a solid base for bark development. Do not be shy here. A good thick rub coat means a beautiful crust.

Place the corned beef brisket fat side up directly on the smoker grates. Insert your leave-in probe thermometer into the thickest part of the flat, making sure the probe tip is centered in the meat and not touching any fat deposits. Close the lid and walk away. Resist the urge to open the lid for at least the first 2 hours. Every time you open that lid you are losing heat and smoke. Let the low and slow process work. You are aiming to build a solid bark on the exterior and allow the smoke to penetrate deep into the brined meat during this first phase of the cook.

Monitor your smoker temperature using a reliable ambient thermometer. Keep it locked at 225 degrees Fahrenheit, adjusting your intake and exhaust vents as needed on a charcoal unit, or adjusting the controller on a pellet grill. At around the 2.5 hour mark, check the smoke output. You want a thin blue-gray smoke, not thick billowing white smoke. White smoke means incomplete combustion and will impart bitter flavors into your meat. Add a fresh wood chunk if your smoke output has dropped off significantly. The internal temp of the brisket should be climbing steadily through the 140 to 150 degree range at this point.

When the internal temp hits 160 to 165 degrees Fahrenheit, you will likely hit the stall, that maddening plateau where evaporative cooling from the meat surface matches the rate of heat being absorbed and the temp appears to stop rising for an extended period. This is completely normal and is your cue to wrap. Pull the brisket off the grates and wrap it tightly in a double layer of pink butcher paper or heavy duty aluminum foil. Butcher paper allows a little breathability and helps preserve more bark texture than foil. Return the wrapped brisket to the smoker and reinsert your probe thermometer through the wrap.

Continue smoking the wrapped brisket until the internal temp reaches 200 degrees Fahrenheit. At this point, mix together the whole grain Dijon mustard and brown sugar in a small bowl for the optional glaze. Unwrap the brisket carefully, brush a thin even layer of the glaze over the entire top surface and sides, and return it to the smoker unwrapped for a final 30 to 45 minutes. This final unwrapped phase lets the glaze caramelize and the bark firm back up after being wrapped. Pull the brisket when the internal temp reads 203 to 205 degrees Fahrenheit and a probe or skewer slides into the thickest part with almost zero resistance, like pushing into soft warm butter.

Rest the meat. This step is non-negotiable. Wrap the finished brisket back in a fresh layer of butcher paper, then wrap that in a thick towel, and place it in an empty cooler for a minimum of 45 minutes and up to 2 hours. Resting the meat allows the muscle fibers to relax and the juices that were driven to the center during cooking to redistribute evenly throughout the slice. If you cut into it straight off the smoker you will lose a significant amount of that hard-earned moisture. When the rest is complete, unwrap and slice against the grain into pencil-thick slices using a sharp slicing knife. Look for that deep red smoke ring running through the first quarter-inch of the meat and a dark, peppery, caramelized bark on the exterior.