Grease bottom and sides of 13 x 9 in pan.
Line with parchment paper and lightly butter the paper.
In a double boiler, melt white chocolate chips (stir frequently).
Once melted, add the milk chocolate chips and stir to melt, blending the two types of chocolate.
When chocolate is blended together, add the entire jar of peanut butter and stir until blended.
Pour into pan and spread evenly.
Refrigerate for 1/2 hour then remove and lightly score. Return to refrigerater until the chocolate sets (about 2 hours). Remove and cut into squares and store in a plastic container in the refrigerator.