Cream together 1/2 c. butter, sugar and brown sugar in a stand mixer until smooth. Add egg and vanilla.
In a separate bowl, whisk together graham cracker crumbs, flour, salt and baking powder.
Slowly add the dry mixture to the wet mixture on low speed until combined.
Spread dough into a greased 9x9" glass baking dish. Bake 20 minutes at 350°F, or until lightly golden on top. Allow to cool.
Using an electric hand mixer, mix peanut butter, powdered sugar and 4 tablespoons of butter together. Press evenly onto cookie layer.
Place chocolate chips and 4 tablespoons of butter in a microwave-safe bowl. Heat for 30 seconds, stir, heat for 30 more seconds, and stir again till smooth and melted. Pour over peanut butter layer.
Allow to cool completely. Cut into bars to serve.
Recipe adapted for Hormel Foods and used with permission from Cupcake Diaries