1. In a small bowl, sprinkle gelatin over 1/2 cup water; set aside. In a small saucepan, combine zest, 3/4 cup juice and the grated ginger. Bring to a boil. Let cool 15 minutes.
2. Meanwhile, in a food processor, pulse together cranberries and sugar until coarsely chopped. Transfer to a medium saucepan and add remaining 3/4 cup juice. Bring to a boil. Reduce to a simmer and cook, stirring occasionally, until cranberries are just softened, about 15 minutes. Remove from heat. Add gelatin and stir until completely dissolved. Strain orange ginger mixture through a fine mesh sieve into cranberry mixture, pressing to extract all the juices (discard pulp).
3. Coat a 1 quart mold with cooking spray and fill with cranberry mixture. Cover and refrigerate at least 6 hours or overnight.
4. To unmold, quickly dip outside of mold several times into very warm water. Loosen edges with a knife and turn onto a serving platter. Garnish with zest and candied ginger, if desired. Makes 8 to 10 servings.