Place 2 cups of peach slices and water in container or an electric blender or food processor. Cover and process until smooth. Pour pureed mixture into a medium saucepan.

Combine sugar and cornstarch. In saucepan, add sugar mixture to peach puree; stir well. Cook over medium-high heat 5 minutes or until mixture is thickened and clear, stirring constantly. Remove from heat. Add butter and almond extract, stirring until butter melts. Let cool.

Arrange remaining 3 cups of peach slices in baked pastry shell. Pour glaze mixture over peach slices. Chill thoroughly. Serve with sweetened whipped cream.