1. Preheat oven to 350°. Stir together iced tea mix and 2 Tbsp. water in a large bowl. Whisk in sweetened condensed milk and next 5 ingredients until blended. Place Gingersnap Crust on a baking sheet; pour in milk mixture.
2. Bake at 350° for 20 to 25 minutes or just until filling is set. Cool completely on a wire rack (about 1 hour). Cover and chill 4 to 24 hours. Remove tart from pan, and place on a serving dish.
3. Beat cream and sugar at medium speed with an electric mixer until stiff peaks form. Pipe or dollop on top of tart; garnish, if desired.
*2 (4-oz.) packages ready-made mini graham cracker piecrusts may be substituted.
Note: You may also bake this tart in a 14- x 4-inch tart pan with removable bottom; increase bake time to 25 to 28 minutes or until filling is set.