In small bowl, stir together cream cheese, confectioners sugar and 1 teaspoon water. Gently spread cheese mixture over bottom and up sides of pie shell in a thin layer; set aside.
Measure 1 cup of the strawberries and set aside. In a large bowl, combine the remaining strawberries with the blueberries and raspberries.
In a medium-size saucepan, thoroughly mash reserved 1 cup strawberries. Add 3/4 cup water and bring to a boil over medium heat. Continue cooking at a low boil for 5 minutes. The berries will be very soft and seem almost dissolved. Remove from heat.
In small bowl, blend granulated sugar and cornstarch. Stir into cooked strawberry mixture. Return pan to stove and cook over medium heat, stirring constantly, until sugar is dissolved and the mixture has come to a full boil and looks translucent. Remove from heat and stir in lemon juice.
Pour cooked strawberry mixture over berries in large bowl; gently stir to coat berries. Pour into prepared crust. Refrigerate for at least 4 hours, or overnight.
To serve, garnish with vanilla ice cream and lemon zest, if desired. Makes 8 servings.