Preheat oven to 350 degrees Fahrenheit (175 degrees Celsius). Grease a 9×13-inch (20×30-centimeter) baking pan and set aside.

In a large mixing bowl, combine flour, sugar, oil, peanut butter, vanilla, egg, and egg yolk. Mix to form a crumbly dough. (I found it easiest to do this with my hands.)

Press three-quarters of the dough into the prepared pan. Use the bottom of a measuring cup to smooth it out. Spread a thin layer of peanut butter over the entire surface. Set aside.

Add caramel chips and brown sugar to remaining dough in bowl. Mix to form crumbs. Spread over dough in pan to form a thick layer.

Bake for about 35 minutes, until set.