Combine and set aside:

2 tsp. cornstarch
2 tsp. water
1 tsp. lemon juice

Boil until they pop:

1 cup fresh blueberries
5 T. water

Add to the cooked berries, and heat until thickened:

1 T. butter
3/4 cup sugar
pinch salt
cornstarch mixture

Remove from heat and add 3 cups fresh berries.
Pour into baked pie shell.