Butterfly the pork loin lengthwise, cutting halfway through so it opens like a book; lay it flat on a cutting board.
Melt butter in a skillet, sauté the onion until soft, add apples and sage, then fold in the bread cubes and broth. Cook 3 minutes and cool slightly.
Spread the stuffing evenly down the center of the opened loin, leaving 1 inch from the edges.
Roll the loin tightly back into a cylinder and tie with butcher twine every 2 inches to seal the filling inside.
Mix mustard, salt, pepper, garlic powder, and paprika; rub all over the tied loin.
Preheat smoker to 225°F using oak or hickory wood.
Place the loin on the grate and smoke for 2.5–3 hours, or until the internal temperature hits 145°F at the center of the thickest part (away from the filling).
Remove from the smoker, tent loosely with foil, and rest for 10 minutes.
Slice between the twine sections and serve while warm.
Tie It Tight
Secure knots on the seam side so they don't show on the sliced edges. If the filling starts to leak during smoking, tent it loosely with foil to prevent it from drying out. A meat thermometer inserted perpendicular to the loin's length ensures you hit the right temp without hitting the stuffing.
FAQ
Can I stuff the pork loin ahead of time?
Yes. Butterfly, stuff, tie, and refrigerate up to 12 hours before smoking. Pull it out 30 minutes before the smoker is ready so it cooks evenly. Don't skip the rest—it keeps the meat tender and the juices inside.