This has to be one of the best recipes for blueberry squares... taken my "Favorite Summertime Recipes" folder! You may use all blueberries, and the larger amount of cornstarch, if you prefer a more "gelatinous" filling, rather than a bit loose. If you follow directions carefully, you will have the most fantastic blueberry squares... I promise! Don't forget, chill for 30 minutes before baking! Please, do the crust only in the processor otherwise it will not have good results! Prep time includes chilling time of 30 minutes. Even better...use 2 cups blueberries with 1 cup raspberries if desired!