cups juice drained from berries
Heat juice in double boiler. Mix cornstarch and sugar. Add to juice and cook over medium heat until thickened (about 10 minutes). Stir frequently. Add margarine and the berries. Line a 7x9x2 inch baking pan with pastry rust. Pour in berry mixture. Top with pastry crust and prick a few holes in crust with fork. Bake at 450 degrees for 40 minutes.