Put the water and ginger juice into a medium saucepan and bring to a boil over medium high heat. Add the chopped chocolate and ground ginger and whisk until the sauce is smooth. Pour into a decorative bowl and serve immediately. The sauce will stay liquid for up to 2 hours. Serve with fresh berries, fresh fruit chunks and marshmallows.
Keep fresh ginger in the freezer. Break off a large knob, peel it and let it thaw. Once thawed the juice can be squeezed out of the ginger.