Chocolate Peanut Butter Bars

2 1/2 cups graham cracker crumbs
1 cup peanut butter
1 cup butter, melted
2 cups semisweet chocolate chips
2 3/4 cups confectioners' sugar
In a medium bowl, stir together graham cracker crumbs, confectioners' sugar, peanut butter and melted butter.
Press firmly into the bottom of a 9x13 inch pan.
Melt chocolate chips and shortning over a double boiler or in the microwave, stirring occasionally.
Spread melted chocolate over the crumb crust.
Chill for about 5 minutes, then cut into bars before the chocolate is completely set, then chill until ready to serve.
For variation, make over a batch of rice crispy treats.