Clean ducks. Wipe dry and place each duck on a “beer-can chicken” stand. Set in a cool room in front of a fan for 4 hours to dry. (See note.) Bring a large pot with water to boil, and add ginger, scallion, honey, vinegar, and sherry. Boil 10 minutes, then pour in the dissolved cornstarch, stirring constantly.
Place one duck in boiling water, count to five and remove. Place the second duck in boiling water, count to five and remove. Repeat for 10 minutes. Place ducks on “beer can” racks again, in front of fan, for 6 hours until thoroughly dry. Turn every 30 minutes.
“Pre-heat” La Caja China with 10lbs of charcoal. If you don't know what a Caja China is, check out my blog. When all coals are covered in white ash, oil the roasting rack and place ducks, breast side up, on rack. Place the rack in the roasting pan with 2 inches of water in bottom, and close up the box, and add another 5lbs of charcoal. You goal temperature inside the box is 350 degrees. Roast 20 minutes.
Turn ducks, add 5lbs of charcoal, and roast 20 minutes more. Turn breast side up again. Roast 5 minutes more, until crispy and browned to your liking. Remove ducks from La Cajita China and allow to rest 10-15 minutes.
Use sharp knife to debone. Serve meat and skin immediately on a pre-warmed dish. The duck is eaten hot with hoisin sauce rolled in Mandarin Crepes. Garnish with diced scallion. Each duck serves 4 to 6.
A note on drying: I set my ducks up on “beer-can chicken” stands (instead of hanging them by the necks – the traditional method), in front of a fan, and turned them every 30 minutes. Worked perfectly!