Put all liquid ingredients and sugar in a tall stock pot and bring to boil. Add duck and reduce heat. When boiling again, turn down to a simmer and skim. Add the rest of the remaining ingredients, except bok choy. Taste for seasoning. It should have an inherent sweetness to the liquid. If not, add more brown sugar. Simmer slowly for 2 to 3 hours, or until duck is very soft. For the last 10 minutes of cooking, add the bok choy. Carefully remove duck and bok choy. Strain the liquid and reduce until a light syrup is achieved. Glaze duck and garnish with sliced scallions.