1 to 1-1/2 quarts fresh or frozen blackberries
2 cups (about) sugar
6 Tablespoons cornstarch, or
1/2 cup flour
2 refrigerator pie pastries
2 Tablespoons butter or margarine
Combine the blackberries, sugar and cornstarch in a bowl and mix gently. Taste and add additional sugar if desired. Let stand at room temperature for 20 minutes. If using frozen berries, thaw and combine undrained berries with the sugar mixture.
Fit 1 of the pie pastries in a 10-inch deep-dish pie plate. Spoon the berry mixture into the prepared pie plate and dot with butter. Top with the remaining pie pastry, sealing the edge and cutting vents. Bake at 400 degrees for 45 minutes or until golden brown.