01 -
Coat brisket point thoroughly with yellow mustard, then evenly apply Thundering Longhorn seasoning, pressing into all crevices. Preheat smoker to 215°F with a water pan. Place brisket fat-side up on the smoker grate, cover, and smoke overnight (8–10 hours) until internal temperature reaches 165°F.
02 -
Lay out butcher paper and spread half the beef tallow in its center. Place brisket on top, spread remaining tallow over brisket, then wrap tightly in butcher paper. Return wrapped brisket to smoker. Increase heat to 250°F, and continue to cook until internal temperature reaches 203°F. Remove brisket from smoker and rest in a cooler for at least 1 hour before slicing.
03 -
Pierce each russet potato multiple times with a fork. Rub evenly with beef tallow and sprinkle with kosher salt. Wrap each potato in aluminum foil. Bake in a preheated 400°F oven or smoker for 1 hour, or until tender throughout.
04 -
After baking, let potatoes cool slightly, then halve lengthwise. Scoop out potato flesh into a large bowl, leaving a 1/4-inch shell. While flesh is hot, add butter and mash lightly. Fold in sour cream, shredded cheddar, black pepper, and a pinch of salt. Mix just until combined and fluffy without overworking.
05 -
Spoon filling evenly back into potato shells. Place stuffed potatoes on a baking sheet and bake at 400°F for 20 minutes, or until tops are golden and edges lightly crisped.
06 -
Arrange crispy fried onions on each potato, then top with chopped brisket. Drizzle with barbecue sauce and garnish with fresh jalapeño slices. Serve immediately while hot.