Put the cranberry-mango relish in a food processor and process until smooth.
Whip together the cream, sugar and vanilla extract until soft peaks form. Reserve 1/4 cup of the cream in a separate bowl. Fold the puree into the remaining cream until just combined. Fill each red wine goblet 1/2 way with some of the fool and sprinkle with some of the gingersnaps. Fill the goblets the rest of the way with the fool, top with a dollop of the remaining whipped cream and a sprinkling of gingersnap.
Melt butter in a medium saucepan over medium high heat. Add onions and ginger and cook until soft. Add orange juice and brown sugar and cook until the sugar is completely melted and the mixture thickens slightly, 5 to 7 minutes.
Add half of the cranberries and cook until they pop. Add remaining cranberries and cook for 5 minutes. Remove from heat and stir in the mangoes and zest. Serve at room temperature.