Looking for the ultimate cookie? This one, from Jesse Szewczyk’s “Cookies: The New Classics” (Clarkson Potter, $27.50), hits all the buttons. Buttery shortbread. Gooey caramel. Nutty peanut butter. Oh, and rich chocolate ganache.

The shortbread base can be baked several days in advance and stored at room temperature, tightly wrapped in plastic. The caramel and ganache layers should be made the day of assembly.

1 2/3 cups spooned and leveled all-purpose flour

1½ sticks (12 tablespoons) unsalted butter, melted and cooled slightly

¾ cup packed light brown sugar

14-ounce can sweetened condensed milk

¼ cup creamy peanut butter, such as Jif or Skippy

½ cup toasted salted peanuts, coarsely chopped

1 cup (about 6 ounces) semisweet or bittersweet chocolate chips or chopped chocolate

Make the shortbread base: Arrange a rack in the middle of the oven and preheat to 350 degrees. Grease an 8-inch-square baking pan with nonstick pan spray. Line with parchment paper, leaving some overhang on all sides. Lightly coat the paper with pan spray.

In a large bowl, combine the flour, granulated sugar and salt. Add the melted butter, egg yolks and vanilla extract and stir, using a rubber spatula, until a crumbly, moist dough forms that holds together when you squeeze it.

Transfer the dough to the prepared baking pan and press into an even layer using the bottom of a measuring cup or clean hands. Prick the top several times with a fork. Bake until the shortbread is slightly puffed and golden brown at the edges, 23 to 28 minutes. Remove from the oven and set aside to cool slightly.

While the shortbread is cooling, make the peanut butter caramel: In a medium pot fitted with a candy thermometer, combine the brown sugar, butter, corn syrup, sweetened condensed milk, peanut butter, vanilla extract and salt. Cook over medium-low heat, stirring constantly to prevent the bottom and sides from burning, until the mixture reaches 235 degrees, 10 to 12 minutes. The caramel should be thick and slightly darkened in color. Remove from heat and stir in the chopped peanuts. Pour over the still-warm shortbread base and transfer to the fridge for 20 minutes.

As the caramel is cooling, make the chocolate ganache: Combine the chocolate, heavy cream, vanilla extract and salt in a medium, microwave safe bowl. Microwave on high power in 10-second increments, stirring between each, until fully melted, 30 to 50 seconds total.

Pour the chocolate over the caramel and smooth it with an offset spatula or spoon. Let the shortbread set in the fridge for 2 hours, then cut into a 6-by-6 grid to make 36 squares. The cookies will keep in an airtight container in a single layer at room temperature for up to one week.

— From Jesse Szewczyk’s “Cookies: The New Classics” (Clarkson Potter, $27.50)

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