Trim the fat cap to a quarter inch and remove hard fat and silverskin. Pat dry, coat thinly with mustard, and season heavily on all sides with salt, pepper, and the optional garlic powder and paprika. Refrigerate uncovered overnight, or rest at room temperature 1 hour.

Fill the smoke box with a scoop of pellets and press the Woodfire Flavor button. Set the grill to Smoker mode at 225°F, and insert a probe into the thickest part of the flat if available.

Place the brisket fat-side up in the center and close the lid. Smoke at 225°F without opening for the first 2 hours, then check every 45 minutes, spritzing dry spots. Continue until the internal temperature reaches about 165°F and the bark is firm and dark, roughly 3 to 4 hours.

Brush with tallow or broth and wrap tightly in butcher paper or foil. Return to the grill, raise the heat to 250°F, and cook another 2 to 4 hours.

From 200°F internal, probe through the wrap in several spots; it's done when the probe meets almost no resistance, which may take until just past 205°F.

Rest wrapped in a cooler or towels at least 1 hour. Unwrap, separate the point and flat if desired, and slice each against its own grain.