Combine 1 cup of the berries, two third cup water, and lemon juice in a saucepan. Simmer over low heat for about 3 minutes. Strain the berries from the juice. Mix the sugar, cornstarch, and remaining water and add to the hot berry juice mixture. Bring to a boil, stirring constantly. Remove from heat and cool. Put the other 3 cups of berries into a 25 cm baked pir shell and pour the glaze over the top and chill. Great with or without whipped cream.