Line a standard 2 cup muffin tin with paper cupcake liners.
Melt half the chocolate either in a double boiler (the safer method) or in the microwave.
Distribute the melted chocolate into the 12 muffin tins, only barely filling the bottom of each cup. If the chocolate does not lie flat, drop the pan repeatedly on the counter, and it will flatten and smooth itself out. Place the pan in the freezer for 15 minutes.
In the meantime, whip the peanut butter, butter, and confectioners sugar together with a hand mixer until mixed and light. Place small tablespoons of peanut butter into each cup, then drop the pan repeatedly on the counter again so the peanut butter layer is flattened out. Place in the freezer for 15 minutes.
Melt the last half pound of chocolate and portion small spoonfuls of chocolate into the cups, one cup at a time, immediately dropping the pan repeatedly on the counter to flatten each cup. Place peanut butter cups in the freezer for 15 minutes to set the top layer of chocolate.
You can either refrigerate them for a peanut butter cup or more bite, or leave them at room temperature for a creamier softer bite.