In a medium, microwave-safe bowl, combine butter and peanut butter. Heat in the microwave until soft; mix well. Gradually stir in confectioners' sugar until the mixture resembles a soft dough. Spread mixture into 2 pie crusts.
In a small bowl, mix the milk with the instant pudding. Pour over the peanut butter mixture in each crust. Chill until firm.
Top pies with whipped topping when ready to serve.