Instructions

• Preheat oven to 350°F. Line an 8-by-8-inch square baking pan with parchment paper, leaving a 1-inch overhang on two opposite sides.
• In a mixing bowl, beat 1/3 cup unsalted butter (room temperature) and 1/3 cup granulated sugar until light and fluffy, about 2 to 3 minutes. Add 1/2 teaspoon vanilla and 1/4 teaspoon salt and mix until combined.
• Add 1 cup all-purpose flour and mix just until incorporated; the mixture will be slightly crumbly. Add 1 tablespoon whole milk and mix until the dough comes together into a cohesive mass.
• Press the dough evenly into the prepared pan to form a thin, even shortbread layer. Prick the surface all over with a fork or skewer to prevent bubbling.
• Bake for 18 to 22 minutes, or until the edges are lightly golden. Remove from the oven and transfer the pan to a wire rack. Let the shortbread cool completely before proceeding.
• In a small saucepan set over medium-low heat, combine 7 oz caramel bits or unwrapped soft caramel candies, 2 tablespoons whole milk, and 2 tablespoons sweetened condensed milk. Stir constantly until the caramel is fully melted and the mixture is smooth. Remove from heat.
• Stir 3 tablespoons creamy salted peanut butter into the hot caramel until fully incorporated and smooth.
• Sprinkle 1/2 cup coarsely chopped peanuts evenly over the cooled shortbread. Pour the hot caramel-peanut butter mixture over the peanuts and shortbread, spreading it to the edges and corners. Refrigerate the pan until the caramel layer is set, at least 30 minutes.
• Place 5 ounces finely chopped dark or bittersweet chocolate in a heatproof bowl. In a small saucepan, heat 1/2 cup heavy cream and 1 tablespoon corn syrup over low heat until it just begins to bubble around the edges. Remove from heat and pour the hot cream mixture over the chopped chocolate. Let sit 30 seconds, then gently whisk until smooth.
• Pour the chocolate ganache over the set caramel layer and spread it into an even, smooth layer with an offset spatula or the back of a spoon. Chill until the chocolate is firm, at least 30 minutes.
• Use the parchment overhang to lift the layered bars from the pan. Place on a cutting board and cut into 2-inch squares. Wipe the knife clean between cuts for neat edges.
• Store the bars refrigerated in an airtight container or wrapped in aluminum foil for up to 3 days.