In a small bowl combine the BBQ sauce, tomato paste, chili flakes, garlic puree and red wine vinegar. Whisk to combine. Gently score the pork shank and place into a roasting pan, pour in the chicken stock and lightly coat with the first glaze. Roast at 300 degrees covered for 3hrs 20 minutes.
Next, combine the Thai sweet chili, Worcestershire, maple and pineapple juice in a small pot. Lightly boil until thicken.
Remove the roast shank from the oven and place onto a platter, generously coat the shank with the glaze.