In the bowl of a food processor, pulse together flour and sugar to mix. Cut up butter and add butter and shortening. Pulse until crumbly. Add peanut butter and pulse to mix, then add egg yolk and vanilla and pulse so that you have a crumbly dough.
Press mixture firmly into ungreased 15 ½ x 10 ½ x 1 inch jellyroll pan.
Bake for 25 to 30 minutes until golden brown.
Cool slightly.
Make the Chocolate Crunch: Melt chocolate in top of double boiler over boiling water. Stir in crunchy peanut butter and cereal. Spread over bake peanut butter layer and let cool until set.