1. Make and Bake the Shortbread Layer:

• Preheat the oven to 350°F (175°C).
• Lightly grease a 9×13-inch baking pan and line it with parchment paper, leaving an overhang on the longer sides for easy removal later. Set aside.
• In a medium bowl, whisk together the all-purpose flour, powdered sugar, cocoa powder, and salt.
• Pour in the melted salted butter. Stir with a fork or spatula until a soft dough forms and no dry streaks remain.
• Press the dough evenly and firmly into the bottom of the prepared parchment-lined pan.
• Bake for 10-12 minutes, just until the shortbread looks set. The recipe author prefers it slightly underbaked for a less crumbly texture.
• Let the shortbread crust cool completely in the pan on a wire rack.

2. Make the Pretzel Caramel Layer:

• Unwrap all the soft caramels (this is the most tedious part!). Place the unwrapped caramels and the heavy cream in a medium microwave-safe bowl.
• Microwave in 1-minute intervals, stirring well after each interval, until the caramels are completely melted and the mixture is smooth. Be careful not to scorch it.
• Choose Assembly Option:
  • Option 1 (Layered): Pour and spread the warm, smooth caramel evenly over the cooled chocolate shortbread layer. Immediately sprinkle the crushed pretzels evenly over the caramel layer, pressing them in gently.
  • Option 2 (Mixed In): Stir the crushed pretzels directly into the warm caramel mixture until combined. Dollop this mixture over the cooled chocolate shortbread layer and use greased hands or a greased spatula to carefully press it into an even layer.
• Place the pan in the refrigerator or freezer briefly to help the caramel layer set slightly while you make the next layer.

3. Make the Peanut Butter Layer:

• Ensure the ¼ cup of salted butter is properly softened.
• In a medium bowl, combine the creamy peanut butter, softened salted butter, sifted powdered sugar, and vanilla extract.
• Beat with an electric mixer (handheld or stand mixer with paddle) on medium speed until the mixture is creamy, light, and fluffy, about 1-2 minutes. Scrape down the sides of the bowl as needed.
• Retrieve the pan from the fridge/freezer. Spread the peanut butter mixture carefully and evenly over the set pretzel caramel layer.
• Place the pan back in the refrigerator while you make the chocolate ganache topping.

4. Make the Chocolate Ganache:

• Place the semisweet chocolate chips in a medium heatproof bowl.
• Heat the 1 cup of heavy cream in a small saucepan over medium heat or in the microwave until it is hot and just beginning to simmer around the edges (do not boil).
• Pour the hot heavy cream directly over the chocolate chips in the bowl. Let the mixture sit undisturbed for 2-3 minutes to allow the heat to melt the chocolate.
• Gently whisk the mixture, starting from the center and working outwards, until the ganache is completely smooth, glossy, and combined.
• Let the ganache cool for a few minutes at room temperature until it’s no longer warm to the touch but still easily pourable.

5. Add Ganache Topping and Chill:

• Remove the pan from the refrigerator. Pour the slightly cooled chocolate ganache over the peanut butter layer.
• Gently tilt the pan or use an offset spatula to spread the ganache into an even layer covering the entire surface.
• Place the pan back in the refrigerator and chill until the ganache is completely set and firm, at least 20-30 minutes, but longer (1-2 hours) is better for easier cutting. The bars can be chilled for up to 24 hours.

6. Cut and Serve:

• Temper Slightly: If the bars have been refrigerated for more than an hour, let them sit out at room temperature for 15-20 minutes before cutting. This allows the caramel layer to soften just slightly, making cutting much easier and preventing cracking.
• Use the parchment paper overhangs to carefully lift the entire block of bars out of the pan onto a cutting board.
• Use a large, sharp knife to cut the block into squares or rectangles. For the cleanest cuts, dip the knife in hot water and wipe it clean between each cut.
• Serve the bars chilled or at cool room temperature. Store leftovers tightly covered in the refrigerator.