Make filling: Preheat oven to 350°F. Whisk together condensed milk and next 3 ingredients until well blended. Pour mixture into piecrust.
Bake pie, then chill: Bake at 350°F for 15 minutes or until pie is set. Cool completely on a wire rack (about 1 hour). Chill 1 hour before serving.
Top with whipped cream and garnishes: Beat whipping cream at high speed with an electric mixer 2 to 3 minutes or until soft peaks form, gradually adding powdered sugar. Top pie with whipped cream. Garnish, if desired.
