Position the rack on the lower third of the oven and preheat to 450 degrees . Season the pork with salt and pepper. In a small bowl, combine 3 tablespoons hoisin sauce, the honey, 1 teaspoon garlic and the sesame oil; reserve half. Place the pork in a small roasting pan and brush with the other half of the hoisin mixture. Roast until it registers 150 degrees on an instant-read thermometer, about 20 minutes. Transfer to a cutting board to rest.
Meanwhile, in a bowl, combine the butter and remaining garlic. Spread the bread halves with the garlic butter, wrap together in foil and bake for 10 minutes. Open the foil, turn the bread cut side up and bake until toasted, 5 minutes.
In a bowl, combine the remaining 1 tablespoon hoisin sauce and the reserved hoisin mixture. Thinly slice the pork. Add to the bowl and toss to coat. Place the pork on the bread bottom and top with the duck sauce. Set the bread top in place and cut crosswise into quarters.