Prepare the Crust: Line an 8×8-inch square baking dish with parchment paper, allowing excess to hang over the sides for easy lifting. In a medium bowl combine 2 cups crushed pretzels, 3/4 cup melted unsalted butter, and 1/4 cup sugar. Mix until evenly moistened and press the mixture firmly into the bottom of the prepared dish. Use the bottom of a measuring cup to get an even, compact crust. Chill for 20 minutes to set.
Caramel Layer: In a small saucepan over low heat, warm 1 cup caramel sauce and 1/2 cup creamy peanut butter, stirring constantly until smooth and fully combined. Do not let it boil; low heat keeps the texture silky. Immediately pour the caramel-peanut butter mixture over the chilled pretzel crust and spread evenly. Return to the refrigerator and chill for another 30 minutes so the caramel layer firms but remains soft.
Chocolate Layer: In a microwave-safe bowl, combine 1 1/2 cups milk chocolate chips and 1/4 cup heavy cream. Microwave in 20-second intervals, stirring between each, until the chocolate is fully melted and glossy. Pour the melted chocolate over the caramel layer and use a spatula to spread into an even layer. Sprinkle with a pinch of sea salt and additional crushed pretzels for texture and presentation.
Final Chill: Chill the assembled bars for at least 2 hours, or until fully set. This makes slicing clean and easy.
Serve: To serve, lift the bars out of the dish using the parchment overhang. Place on a cutting board and slice into squares with a sharp knife. For neater cuts, chill briefly between cutting portions.
Notes
Store bars in an airtight container in the refrigerator for up to 5 days. For longer storage, freeze in a single layer on a tray until firm, then transfer to a freezer bag for up to 2 months. Thaw in the refrigerator overnight before serving.