Preheat oven to 375 degrees F. Chop up Reese peanut butter cups and refrigerate.
Sift together the flour and baking soda, and set aside.
Cream your butter and sugars. Add egg, egg yolk, and vanilla.
Slowly mix in the flour mixture into the butter mixture, mixing well. Add the chocolate chips and chopped Reese's.
Scoop out the dough, set on a parchment lined cookie tray, and refrigerate for at least half an hour. The longer the better!
Bake for 10 to 12 minutes, or until the edges are golden brown.