Mix walnuts and butter in a 9-inch pie plate until well blended
Press onto bottom and sides of plate
Refrigerate Microwave chocolate and 2 tablespoons of the milk in a large microwavable bowl on High 1 12 to 2 minutes until chocolate is almost melted stirring halfway through
Stir until chocolate is completely melted
Beat in cream cheese sugar and remaining milk until well blended
Refrigerate about 10 minutes to cool
Gently stir in whipped topping until smooth
Spoon into crust
Freeze 4 hours or until firm
Let stand at room temperature about 30 minutes until pie can be easily cut