- In a pot of salted boiling water, poach the roast two hours in simmering water. Drain.
- Meanwhile, in a saucepan, bring all the ingredients to a boil. Reduce for 15 to 20 minutes or until the sauce thickens and only 250 ml (1 cup) is left.
- In a large bowl or in the same pot, coat the meat with the marinade. Set aside.
- Preheat the grill, setting the burners to high.
- Insert the roasting pin through the roast and install on the spit. Season with pepper. Place a roasting pan or a large old aluminum plate filled with water directly on the grill under the roast. Reduce the temperature of the grill to low heat. Roast for about 2 hours or until meat is tender. Baste meat with the marinade every 15 minutes. Let cool for 10 minutes.
- Remove the string, undo the roast into chunks or slice.