Cut the pork into long slices approximately 2 to 3 inches thick.
Use a fork to poke each side of the meat (this helps the pork absorb the marinade more effectively).
In a mixing bowl, thoroughly mix together all of the char siu sauce ingredients until the sugar has dissolved into the sauce mixture.
Pour the pork and 3/4 of the char siu marinade (keeping 2 to 3 tablespoons) into a ziplock bag or airtight container.
Massage or mix the marinade into the meat then leave it to marinate for up to 24 hours (or for at least 3 hours).
Roasting & Basting
Preheat your oven to 160°C (140°C, gas mark 3) and line a roasting tray with foil or parchment paper.
After 20 minutes, remove the pork from the oven and brush the basting mixture over the pork then turn it over, brush with the basting mixture and roast for another 20 minutes.
Base the mixture again on both sides (using all the remaining basting sauce) and roast for a final 10 minutes or until caramelised and sticky.
Leave the meat to cool down for 5 to 10 minutes then serve and enjoy!