For the rub:
2 Tbs Chinese five-spice powder
2 Tbs packed dark brown sugar
3 tsp salt
2 tsp black pepper
2 tsp ground coriander
1 tsp cayenne
3kg pork shoulder or similar
For the sauce:
1 cup dark brown sugar
¾ cup hoisin sauce
½ cup soy sauce
1/3 cup rice vinegar
3 garlic cloves, minced
2 Tbs finely grated fresh ginger
1 tsp Chinese five-spice powder
To serve:
Buns or tortillas
Stir together spices in a small bowl.
Remove pork from refrigerator and put in a large roasting pan. Trim surface fat from pork, then rub all over with spice mixture.
Let pork stand at room temperature 30 minutes.
Roast pork:
Heat oven to 180°C
Cover pork roast with a sheet of baking paper, then cover roasting pan tightly with foil.
Roast 1 hour.
Carefully loosen foil, lift up parchment, and pour half the sauce over pork. Tightly cover pork again and roast 1 more hour.
Turn pork over and pour remaining sauce over it, then tightly cover again.
Continue to roast, basting every hour with pan juices, 3 hours more, or until fork-tender (a meat fork should insert easily) and an instant-read thermometer inserted 4 cms into centre of meat (avoid bone) registers 90°C
Uncover pork, then baste with pan juices and roast until meat is browned, 30 to 45 minutes.
Transfer to a cutting board. When meat is cool enough to handle, coarsely shred it, using 2 forks, and transfer to a large bowl.
While pork is cooling, pour pan juices into a large measuring cup and let stand until fat rises to top, then spoon off and discard fat. Drizzle meat with some pan juices and serve remainder on the side.
Serve pork and Vietnamese slaw on buns or in tortillas.
Notes:
Pork can be roasted and shredded 3 days ahead. Cool meat and pan juices separately, uncovered, before chilling, covered. Fat is easiest to remove from pan juices when chilled.
If using flour tortillas, toast on a hot griddle or directly on grill rack of a gas grill heated to medium, until puffed slightly and browned in spots, about 15 to 30 seconds on each side, and immediately slide inside a folded towel to keep warm.