For the Dough

• 1¼ cups (280 g) unsalted butter, at room temperature
• ¼ cup (60 ml) rendered bacon fat, at room temperature
• ¾ cup (150 g) sugar
• 1½ teaspoons pure vanilla extract
• 3 cups (375 g) all-purpose flour

For the Filling

• 4 tablespoons (55 g) unsalted butter
• 1 cup (200 g) sugar
• ½ cup (120 ml) evaporated milk or heavy cream
• 1 cup (240 ml) smooth peanut butter
• 1 (7½-ounce/213-g) tub marshmallow cream
• 1 teaspoon pure vanilla extract
• 1 (13.4-ounce/380-g) can dulce de leche
• 2 cups (300 g) salted peanuts
• 1 cup (110 g) Bacon Bits
• 2 cups (350 g) semisweet chocolate chips

Preheat the oven to 350°F (175°C). Line a 9 by 13-inch (23 by 33-cm) metal or glass baking pan with parchment paper, leaving an overhang on the two long sides. Spray the parchment and sides of the pan lightly with nonstick spray.

Make the dough: Combine the butter, bacon fat, and sugar in the bowl of a stand mixer fitted with the paddle attachment and beat on high until light and fluffy, about 3 minutes. Add the vanilla and beat for 10 seconds.

Reduce the mixer speed to low and gradually add the flour, mixing until just incorporated. Press or spread the mixture into the bottom of the prepared pan. Bake until lightly golden brown, 25 to 30 minutes. Remove from the oven and let cool on a wire rack for 15 minutes while you prepare the filling.

Make the filling: Put the butter in a medium saucepan over high heat and cook until melted. Whisk in the sugar and evaporated milk and bring to a boil over medium-high heat. Continue to boil, whisking occasionally, for 5 minutes. Remove from the heat and whisk in ¼ cup (60 ml) of the peanut butter, the marshmallow cream, and the vanilla until smooth. Pour the mixture evenly over the prepared crust, transfer to the freezer, and chill until firm and cold, about 15 minutes.

Meanwhile, put the dulce de leche in another medium saucepan over low heat and cook until it begins to melt. Stir in the peanuts and cook for 2 minutes. Remove from the heat and fold in the bacon bits. Remove the pan from the freezer and pour the dulce de leche over the peanut butter layer. Return to the freezer until firm and cold, about 15 minutes.

While the dulce de leche layer is setting, pour 1 inch (2.5 cm) of water into a medium saucepan or pot and bring to a simmer over low heat. Place a heat-safe bowl on top of the pot so that the bottom of the bowl is not touching the water.

Add the chocolate to the bowl and stir occasionally with a spatula until smooth and melted. Whisk in the remaining ¾ cup (180 ml) peanut butter until smooth. Remove the pan from the freezer again and pour the chocolate mixture evenly over the top. Return to the freezer until chilled, about 20 minutes.

Cut into bars while cold and refrigerate any leftovers, tightly sealed in a container, for up to 3 days.