1. Whisk together evaporated milk and next 2 ingredients in a bowl 2 minutes or until mixture is thickened.
2. Beat cream cheese and vanilla at medium speed with an electric mixer until fluffy. Add lemonade concentrate, beating until smooth; add milk mixture, and beat until blended. Pour into crust. Cover and chill 8 hours or until firm. Dollop each slice with whipped topping. Garnish, if desired.