In medium bowl, beat whipping cream, 1/4 cup powdered sugar and vanilla until soft peaks form; set aside. In large bowl, beat cream cheese and peanut butter until light and fluffy. Add 1 cup powdered sugar and milk; beat until smooth and creamy. Fold in 1 1/2 cups of the whipped cream. Spoon into cooled pie crust; spread evenly. Refrigerate at least 4 hours before serving.