Preheat oven to 350°F.
Whisk together condensed milk and next 3 ingredients until well blended.
Pour mixture into piecrust.
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.
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.
