So there's this thing here in Britain called Millionaire's Shortbread. It's like the triple threat of bar cookies - rich buttery shortbread base, slathered with sticky caramel, and topped with chocolate. But if your not content with millions, go for billions. And how might one do that? By adding chunky peanut butter to the mix.
Making this bar cookie is multi-step, but quite simple. The first thing to do is to make dulce de leche. This is basically a milky carmel, created by cooking milk and sugar over a low flame for hours. Chez Pim has a lovely homemade recipe or you can do the boil-a-whole-can-of-condensed-milk method. Keep in mind that this method is not recommended as the can could explode if it is not immersed in water the entire time. For me both methods work well, but either way do it a day in advance so it has time to chill. Also, if decide to do the boil-the-can method, let it sit at room temperature for a few hours before you attempt to open the can.
Once the dulce de leche is chilled, make your shortbread. My Scottish Shortbread recipe is found at the end of this post and if you double the recipe it is perfect for and 8x8 inch pan. Instead of cutting the dough into desired shapes as the recipe suggests, just roll it out between two sheets of parchment (its a bit sticky) to cover the 8x8 inch pan. Do not overbake, if anything underbake a touch - it will make cutting this bar at the end so much easier. This shortbread does not spread in the oven so I find it is easier to flip my baking tray over. Then bake the shortbread on the backside of the pan, like a tabletop. Place a cut piece of parchment that will go in between the shortbread and the pan. This keeps you from having to unearth the shortbread out of the pan or deal with any breakage. Once your shortbread is cooked, set aside to cool completely.
At this point take your chilled dulce de leche and put 3/4 cup into a stand mixer with the paddle attachment. Paddle for 30 seconds. Then add 1/2 cup of peanut butter - your favorite kind. I went with chunky, but if you prefer smooth, that's fine. Paddle together for 1 minute. Then use a small offset spatula and spread the mixture evenly all over the shortbread. Put in fridge to chill while you make the chocolate top.
For the chocolate layer - melt in a double boiler 8 oz of semi-sweet chocolate with 3 Tbs of heavy cream and 1 Tbs + 1 tsp of butter. Once its smooth and melted together, spread evenly over the dulce de leche + peanut butter layer. Let chill for about an hour. Cut into squares using a hot knife.