Preheat oven to 220C. Rinse chicken under cold water. Trim away excess fat from inside and outside the cavity and discard. Trim off neck,parson's nose and winglets,freeze and use in stock. Pat chicken thoroughly dry inside and out with kitchen paper.
Combine salt with the five-spice powder and rub inside chicken cavity. Stuff cavity with the crushed garlic and spring onion.
Rub the outside of the chicken with sesame oil. Place breast-side up,on a wire rack in a roasting tin and pour enough boiling water into the tin to reach a depth of 5mm.
Roast for 15 minutes,then reduce oven temperature to 180C and continue roasting for 35 minutes,adding more boiling water to the tin if it begins to dry out. To test if the chicken is ready,pierce the thigh with a skewer;if the juices run clear the chicken is cooked.
Remove chicken from oven and allow to rest in the tin,loosely covered with foil,in a warm place for 15 minutes. Reserve cooking juices in tin.
When you're ready to serve,use a sharp knife or cleaver to cut the chicken in half through the breastbone. Transfer the garlic and spring onion from the cavity to a small saucepan,along with any cooking juices from inside the bird. Add reserved juices from roasting tin,scraping any cooked-on bits from the base of the tin into saucepan. Place saucepan over high heat,add soy sauce, hoisin and plum sauce and cook for 1-2 minutes,just to heat through and reduce slightly. Pour into a small serving bowl.
Chop chicken Chinese-style and arrange on a serving platter. Serve with the sauce on the side for dipping.
Serve withKylie Kwong's Asian-style coleslaw.