In a large saucepan, add water, half the plums, 1/2 of the mixed fruit, rhubarb, sugar, spices and vanilla. Bring the mixture to boil. Reduce the heat to low, cover, and simmer slowly until the fruit is tender about 10 minutes.
Discard the cinnamon stick, return the liquid to boil uncovered, until it reduces reduced by half, stirring occasionally.
Whisk in corn starch and continue cooking until mixture thickens. If you are using very seeded fruit (like blackberries) you'll want to strain the mixture before pureeing. Puree mixture in food processor. Chill for at least an hour and serve with remaining fruit on top.
