Preheat the oven to 350 degrees F. Set out a 9X13 inch baking dish and line it with parchment paper.
For the Crust: Cut the butter into cubes. Place the butter cubes, brown sugar, egg yolk, cake flour, and salt in a large food processor. Pulse unto a fine crumb. Then add 4 teaspoons cold water and pulse again until the dough comes together. It should still be crumbly, but should stick together with pressed. If needed, add another teaspoon of water and pulse again.
Dump the dough into the prepared pan. Press into a tight even layer. Then bake for 25-30 minutes, until the top is golden.
For the Caramel Peanut Butter Layer: In a microwave-safe bowl, add the powdered sugar, peanut butter, dulce de leche, and butter. Microwave for one minute. Stir to combine. Microwave one more minute, if needed, then stir until the mixture is smooth. Then stir in the vanilla extract.
Scoop the caramel peanut butter fudge over the cookie layer. Smooth into an even layer. Chill until the chocolate layer is ready.
For the Chocolate Topping: In a clean microwave-safe bowl, combine the chocolate chips, heavy cream, and corn syrup. Microwave in one minute increments, stirring in between, until the chocolate ganache is very smooth. Then pour over the caramel layer and spread into an even layer.
Chill for at least 2 hours to set. Then lift the entire sheet of bars out of the pan, by the edges of the parchment paper. Cut into 12 large bars or 30 small bars.
Pro Tip: For really neat-cut sides, chill the bars for longer so the bars are hard when cutting. Then leave out on the countertop to soften.