Hull, wash in cold water, and thoroughly drain berries. Crush enough (with potato masher) to make 1 cup.
Combine sugar and cornstarch. Add crushed berries and water. Cook over medium heat, stirring constantly, until mixture comes to a boil. Continue cooking and stirring over low heat for 2 minutes. The mixture will be thickened and translucent. Remove from heat and stir in butter. Cool.
Place whole berries in pie shell, reserving a few choice ones for garnishing. Pour cooked mixture over berries and chill at least 2 hours. Serve topped with whipped cream sweetened with confectioner's sugar. Garnish with remaining strawberries.
Variation: Strawberry Cheese Glace Pie: Combine 1 3-ounce package cream cheese (room temperature) with 1 tablespoon milk and spread over bottom of pie shell before adding berries.