Rinse, trim and quarter duck; pat dry. Place skin side down on a roasting pan, sprinkle with salt, and pepper. Bake in a 350° F oven for 50 minutes.
Meanwhile, in a saucepan combine together ginger ale with sliced ginger root; bring to a boil, reduce heat and simmer until reduced to about 1 cup. Add in orange juice, brown sugar, orange marmalade, prepared brown mustard, chopped green onions, and 2 Tbsp brandy. Bring to a boil, reduce the heat, and simmer until the mixture is a thin syrup, about 20 to 25 minutes. Remove the ginger.
Turn the duck skin side up, drain any fat, and baste thoroughly with the sauce. Return to the oven and bake another 45 minutes, basting every 10 minutes. Add 3 Tbsp brandy to the remaining sauce and simmer until thickened. Remove duck to a serving platter and pour on the sauce. Garnish with sliced orange.
Servings: 4