Preheat your oven to 350F. While it's heating, line an 8-inch square baking pan with aluminum foil, ensuring to leave an overhang for easy removal later. This is a crucial step to make cleanup easier!
In a medium mixing bowl, combine the unsalted butter, all-purpose flour, confectioners’ sugar, cornstarch, and vanilla extract. Use a pastry cutter or your fingers to mix until you achieve a sandy, crumbly mixture. This consistency is important for the crust.
Transfer the crumbly mixture to the prepared pan. Using your fingertips, press down the mixture to form an even flat layer for the crust. Be sure to distribute it evenly to ensure consistent baking.
Pierce the crust with a fork haphazardly in a dozen places. This lets steam escape while it bakes, preventing a soggy crust. Bake for 12 to 15 minutes until the crust is just set. It should remain pale, not golden, and have a soft, crusted surface.
While the crust bakes, prepare the peanut butter filling. In a medium microwave-safe bowl, melt the butter for about 1 minute. Add the creamy peanut butter, confectioners’ sugar, and the vanilla extract. Stir until the mixture is smooth and well combined.
Once the crust is done baking, you can spread the peanut butter filling over it while it’s still warm. This helps the filling to adhere better. The filling will be thick, so take time to spread it evenly without tearing the crust.
Next, pour the salted caramel sauce over the peanut butter filling. It should spread out on its own, but use a knife if needed to ensure it reaches the corners and edges of the pan.
Now, let’s make the chocolate layer. In a clean medium microwave-safe bowl, combine the semi-sweet chocolate chips and vegetable shortening. Heat in the microwave, stopping every 15 seconds to stir until smooth and melted.
Pour the melted chocolate over the caramel layer. If desired, smooth it very lightly with an offset spatula or knife. This adds a nice finish to the bars.
Cover the pan with aluminum foil to prevent any fridge odors from affecting your dessert. Place it in the refrigerator for at least 3 hours, or overnight if you can wait. This chilling time is crucial for setting the layers.
After the bars are chilled, lift them out of the pan using the overhanging foil. Slice into squares or bars. If they’re too cold, let them sit at room temperature for a few minutes before cutting.
Store any leftover bars in the refrigerator for up to 10 days or in the freezer for up to 3 months. Just remember, they might lose some snap if stored too long, but they’ll still be delicious!
