01 -
Trim excess fat from the brisket and pat dry. Apply a thin layer of mustard over all sides as a binder, then coat generously with the brisket rub. Cover and refrigerate for 1 to 2 hours.
02 -
Preheat pellet smoker to 210°F. Place the brisket fat side up on the grate. Smoke with hickory wood pellets for 9–10 hours until the internal temperature reaches 165–170°F.
03 -
Transfer the brisket to butcher paper. Drizzle with apple cider vinegar and beef tallow. Tightly wrap and return to smoker. Increase temperature to 250°F and continue smoking until internal temperature reaches 204–206°F.
04 -
Remove the brisket from the smoker and let rest, wrapped, at room temperature for 2 to 3 hours.
05 -
In a skillet over medium heat, add avocado oil and half the butter. Sauté diced onion for 10–12 minutes, stirring frequently, until deeply caramelized. Set aside.
06 -
Slice the rested brisket thinly. On one slice of bread, layer caramelized onions, sliced brisket, Colby Jack cheese, provolone cheese, and fried crispy onions. Drizzle with barbecue sauce and top with another bread slice.
07 -
Melt remaining butter in a cast iron skillet over medium heat. Place sandwiches in skillet and toast for 2–3 minutes per side until golden brown and cheese is melted. Serve immediately.