Mix 2 sticks of butter, powdered sugar, peanut butter, and graham cracker crumbs. Spread mixture on the bottom of the pan.
Melt chocolate and spread over mixture in pan. Let set in a cool place. Remove
from pan and cut into desired shapes.
You can melt the chocolate either in the microwave or in a double boiler.
In a Microwave Oven
Place coarsely chopped chocolate in a microwave-safe container and microwave at MEDIUM (50 percent power) for 1 1/2 to 4 minutes, until the chocolate turns shiny. Remove the container from the microwave and stir the chocolate until completely melted. Stir milk and white chocolates after about 1 1/2 minutes. Because of their milk proteins, they need to be stirred sooner than dark chocolate. (If overheated, these chocolates may become grainy.)
In a Double Boiler
Place coarsely chopped chocolate in the top of a double boiler over hot, not simmering, water. Melt the chocolate, stirring until smooth. Remove the top part of the double boiler from the bottom.