Roll dough into a 12-inch circle; fit into a 9-inch pie plate coated with cooking spray. Fold edges under, and flute. Bake piecrust according to package directions. Cool completely on a wire rack.
Combine milk and the next 4 ingredients (through ginger) in a medium, heavy saucepan over medium-high heat; cook until the mixture reaches 180° or until tiny bubbles form around edge. Remove from heat. Add tea bag; cover and let stand for 15 minutes. Strain the mixture through a sieve over a bowl, and discard solids. Return milk mixture to pan, and cook over medium-high heat until the milk reaches 180° or until tiny bubbles form around edge.
Combine sugar, cornstarch, salt, and eggs in a large bowl, stirring well. Gradually add the hot milk mixture to sugar mixture, stirring constantly with a whisk. Return milk mixture to pan, and cook over medium heat 10 minutes or until thick and bubbly, stirring constantly. Remove from heat; stir in butter.
Place pan in a large ice-filled bowl for 10 minutes or until filling cools, stirring occasionally. Spoon mixture into crust; cover surface with plastic wrap. Chill 3 hours or until set; remove plastic wrap. Top pie with whipped topping; garnish with ground cinnamon.