In a glass dish, mix the bourbon, soy sauce, sugar, lemon juice and rosemary sprigs. Add the pork and turn to coat. Let stand for 1 hour, turning the pork every 30 minutes.
Assemble the smoker by spreading 1/2 cup small, dry hardwood chips over the bottom of the smoker, then placing the drip tray and rack directly on the chips. (To jury-rig a smoker, line a wok or disposable aluminum baking pan with heavy-duty foil and spread with dry wood chips; top with another layer of foil—to catch drips—and a rack. Cover the wok or pan by sealing it tightly with a lid or sheet of foil.)
Preheat the oven to 375°. In a well-ventilated area, set the smoker over high heat. When smoke rises from all sides, set the pork on the rack; reserve 1/2 cup of the marinade. Cover and smoke for 40 seconds; remove from the smoker.
In an ovenproof skillet, heat the oil until shimmering. Add the pork and season with salt and pepper. Cook over moderate heat until browned all over. Transfer the pork to the oven and roast until pale pink in the center, 15 minutes. Transfer the meat to a carving board and let rest for 5 minutes.
Pour off the oil and set the skillet over high heat. Add the reserved marinade and the broth and boil, scraping up any browned bits in the skillet, until reduced to 2/3 cup, 5 minutes. Remove from the heat, swirl in the butter and season with salt and pepper. Stir in the chopped rosemary.
Slice the pork 1/3 inch thick. Serve with the pan sauce and the Smoked-Onion Soubise.