FOR RUB AND PORK:

2 tablespoons Chinese five-spice powder
2 tablespoons packed dark brown sugar
3 teaspoons salt
2 teaspoons black pepper
2 teaspoons ground coriander
1 teaspoon cayenne
1 (8- to 10-pound) bone-in pork shoulder roast (preferably butt end) without skin

FOR SAUCE:

1 cup packed dark brown sugar
3/4 cup hoisin sauce
1/2 cup low-sodium soy sauce
1/3 cup unseasoned rice vinegar
3 garlic cloves, minced
2 tablespoons finely grated fresh ginger
1 teaspoon Chinese five-spice powder

FOR ASSEMBLY:

16 hamburger buns, split and toasted, or 16 (6- to 7-inch) flour tortillas (optional; see Cooks’ Notes)
Vietnamese Slaw