Bring to a gentle boil; cook and stir 2 minutes. Remove from heat; stir in butter and vanilla until butter is melted. Cool 5 minutes, stirring occasionally. Pour into crust; sprinkle with confectioners sugar. Chill 30 minutes or until set. TOPPING: Press 2 1/2 cups of blueberries through a sieve; set aside 1 cup of the juice (add water if necessary to make 1 cup of liquid). Discard pulp. In a saucepan, combine sugar and cornstarch. Gradually stir in blueberry juice; bring to a boil. Boil 2 minutes, stirring constantly. Remove from the heat; cool 15 minutes. Gently stir in the remaining 2 1/2 cups of berries; carefully spoon over filling. Chill 3 hours or until set. Store in the refrigerator. From the recipes files of suzy@gannett.infi.net ----