Because this fresh summer-fruit dessert feeds a crowd and can be made ahead, it's ideal to serve at your next backyard gathering. Serve it in cups with spoons, or as a sauce for angel food cake or vanilla light ice cream.
Combine first 5 ingredients in a medium saucepan; stir well with a whisk. Add blueberries and mango; bring to a boil, and cook 1 minute or until thick, stirring constantly. Remove from heat; stir in vanilla. Serve warm, or cover and chill.