Blueberry-Raspberry Pie (double crust)

1 c. sugar
2 Tb. cornstarch
2 Tb. quick-cooking tapioca
1/2-1 tsp. cinnamon
1/2-1 tsp. vanilla extract
pinch of salt
8 c. berries (I use frozen unsweetened blueberries & raspberries)
1 Tb. butter

Combine all ingredients except butter and pour into prepared crust in pie pan. Dot with butter and top with top crust. Bake at 350 degrees for 50-60 minutes or until filling is thick and bubbly.