The Pak Cham Kai, go through the process of dipping into boiling water(with incredient like ginger and leek) then go into ice water. Repeat 3x this process. Until the chicken is cooked but not overcook. The ice water prevent overcooking and shrink/tighten the skin (to preserve the sweetness of the chicken).

There are also chicken rice sellers who have specific order for chicken (must be how many months old, weigh how many kg etc) to the supplier.

Ha ya, me too use the spoon to scrap ginger skin!