Triple Berry Pie Filling

Fills a 9" pie with no crowning, or a nice and full 8" pie.

Ingredients:

4 1/2 c frozen berry mix (I used Costco's blueberry-raspberry-blackberry mix)
2/3 c. sugar
1/4 c. cornstarch
1/2 t. cinnamon
2 T. lemon juice
approx. 2 T softened butter to put on top before the top crust

In small bowl mix the sugar, cinnamon and cornstarch well. In larger bowl mix frozen berries and lemon juice, then stir in the mixed dry ingredients. Mix thoroughly. Pour into pie crust. Don't worry if the berries are still frozen. Dot top with butter. Top with crust, crimp edges, make some slits in the crust, protect edges with strips of aluminum foil, put on cookie sheet to catch drips, and bake at 325 degrees F for 40+ minutes. When it is done the filling will bubble a bit through the nicely golden crust. If that is not happening, bake longer. The frozen berries can slow baking down. (It took my last GF pie at least 80 minutes to bake, but it was well worth the wait!)

Note: It might not be a bad idea, when filling a 9" or 10" pie, to increase the berries to 5 1/2 or 6 cups and the sugar cornstarch mixture to around 1/2c. sugar and 1/3 c. cornstarch.
Also, I just figured out that letting the pie cool all the way lets it set up so the filling doesn't run all over the place when cut. Yeah. It takes me a while.