Prepare the duck by cleaning the inside cavity thoroughly and dry with a paper towel.
Mix the salt, sugar and Asian Wok Spice together in a bowl. Rub the mixture inside the duck cavity and ensure the interior is fully coated. Mix the garlic, hoisin and soy sauce in a bowl and pour inside the cavity. Rub in the mixture to ensure good coverage. Insert the ginger and spring onion.
Use a skewer to close the cavity. Wipe the outside of the skin to ensure no sauce is left on the outside of the duck (this is done to avoid burning the skin during roasting).
Bring a big pot of water to boil add the bicarb soda.
Using a balloon pump, carefully pump air between the duck skin and meat. Put the opening of the pump in the neck area underneath the skin. Push a few pumps until you can see the skin balloon up. Take care not to over pump as it might break the skin. Remove the pump and hold on to the neck opening to avoid air escaping. Holding the neck of the duck, plunge the duck into the hot water and then lift out. Repeat a few times and ensure the entire duck is covered. If your pot is not big enough, you can turn the duck upside down and repeat the same process until the entire duck has been submerged. This will tighten the duck skin and is critical to achieving crispy skin.
Air dry the duck on a rack for approximately 30 minutes.
Meanwhile, prepare the glaze. Put all the ingredients into a glass bowl and set the bowl in hot water to help dissolve the maltose syrup. Combine all ingredients to a runny glaze.
Once the duck skin is dry, generously apply the glaze over the skin and ensure the duck is completely coated. Place the duck in a roasting tray and place uncovered in the fridge to dry the duck skin for at least 5 hours or ideally overnight.
When ready to cook, remove the duck from the fridge and return to room temperature for approximately 30 minutes.
Preheat oven 200°C.
Wrap the ends of the duck leg with foil to avoid burning. Cook the duck for 30-35 minutes and once the duck is golden in colour, turn the duck over and reduce heat to 180°C and roast for another 20-25 minutes. Remove from oven and let it rest for 10-15 minutes.
Remove skewer from duck pour the sauce out into a bowl from the duck cavity. Remove the spring onion, onion and ginger and disregard.
