Beat cream cheese and lemon juice on medium speed for 1 minute, or until well combined and fluffy. Place 1c of peanut butter chips and the milk in a bowl - microwave 45 seconds, or until melted. Stir until smooth. Add to cream cheese mixture, and beat on medium 1 minute.
Beat 1/2c of whipping cream in a bowl until stiff - fold into peanut butter mixture. Pour into crust. Cover and refrigerate until firm (1 hour or more).
Combine remaining 1/2 c whipping cream, powdered sugar, and vanilla in a small bowl. Beat until stiff, and spread over pie. Garnish with remaining peanut butter chips. Keep refrigerated until ready to serve.