For the pork, combine char siu sauce, garlic, shallot, soy sauce and red food colouring in a large glass or ceramic bowl.
Add pork and toss to coat. Cover and place in the fridge for 8 hours or overnight to marinate.
Preheat oven to 200°C/180°C fan forced. Line a baking tray with baking paper.
Transfer pork to tray, reserving leftover marinade. Roast for 25 minutes or until cooked through. Baste with reserved marinade. Preheat grill to high. Grill for 2-3 minutes each side or until starting to char. Transfer pork to a clean tray and brush with honey. Rest for 5 minutes. Slice pork.
For buns, put yeast and water in a bowl. Stand for 2 minutes. Add peanut oil. Place sugar, milk powder, baking powder and 375g of the flour in a food processor. With motor running, slowly add yeast mixture until dough comes together. Turn onto a floured surface. Knead for 5 minutes, adding extra flour if necessary.
Place dough in a greased bowl. Cover. Put in a warm place for 1/2 hours or until doubled in size. Cut fourteen 10cm squares of baking paper. Turn dough onto a floured surface. Divide into 14 balls. Roll into a ball in the palm of your hand and place smooth side up onto a paper square.
Repeat with remaining dough. Cover with a damp cloth. Set aside in a warm place for 30 minutes. Fill a wok one-third full with water. Bring to boil over a high heat.
Place 3-4 buns, not touching, in a bamboo steamer. Place steamer over wok.
Steam, covered, for 12 minutes or until cooked through. Repeat with remaining buns.
Combine the hoisin and Sriracha in a small bowl.
Carefully open each bun and fill with pork, cucumber and shallots. Drizzle generously with the sauce.