Combine the peanut butter and powdered sugar until the peanut butter is no longer sticky. You may need a little extra powdered sugar.
Roll the peanut butter into 12 balls, pressing each slightly flat to form patties. Set aside.
Line a mini muffin pan with 12 paper liners. (Greasing the pan does not work well for this, so it's really best to use paper liners here.)
In a double boiler, melt chocolate chips. (To do this, put the chocolate chips in a heatproof bowl, and place the bowl in a pot of boiling water. Ideally, the bowl will not come into contact with water. It's best to use a bowl large enough to prevent the water from getting into the bowl.)
Spoon a small amount of melted chocolate into the bottom of each paper liner.
Press a peanut butter patty into each cup on top of the melted chocolate.
Spoon melted chocolate over top of the peanut butter patty, making sure it gets on the sides of the patty as well, filling the cup to the top.
Place in the freezer for approximately 30 minutes, or until chocolate has hardened.
Allow to sit out for a few minutes before eating. I store these in my fridge or freezer.