The alchemy happens in the oven. Because these slice-and-bake cookies are baked in muffin tins until their bottoms and sides are deeply golden, the butter and sugar brown so completely that they produce the full, nutty, edgily sweet flavor of caramel. A treat! But not the cookies' only treat. Their texture is a delightful mix of crisp and tender, the sign that they're shortbread at heart. And the addition of chopped walnuts and small chunks of chocolate means that they could rightly be called chocolate chip cookies, though perhaps ones that lived briefly in France.

Directions:

1. Working in the bowl of a stand mixer fitted with the paddle attachment. or in a large bowl with a hand mixer, beat the butter, both sugars and the salt together on medium speed until creamy, about 2 minutes. 
2. Beat in the vanilla. Turn off the mixer, scrape down the bowl and add the flour all at once. 
3. Pulse the mixer a few times, just until the risk of flying flour has passed, and then, working on low speed, beat until the flour is almost completely incorporated, a couple of minutes. Don't beat too much-you want the mixture to be more clumpy than smooth. Still working on low speed, mix in the chocolate and nuts. 
4. Then finish incorporating the chunky ingredients with a flexible spatula.
5. Turn the dough out onto the work surface and knead it to bring it together. 
6. Divide the dough in half and shape each hunk into a 6-inch-long log (the rolls will be a scant 2 inches in diameter).
7. Wrap each log well and refrigerate until firm, at least 2 hours. (You can refrigerate the logs for up to 3 days. Or you can freeze them, wrapped airtight, for up to 2 months; let stand at room temperature for about an hour before slicing and baking, or defrost in the fridge overnight.)

When you’re ready to bake:

1. Center a rack in the oven and preheat it to 350°F. (If you can't fit two muffin tins on one rack in your oven, position the racks to divide the oven into thirds.
2. Butter two Stud Muffin tins — you can use bakers' spray, but butter is really nicer for these.
3. One at a time, mark each log at ½-inch intervals and, working with a chef's knife, cut into rounds. 
4. Place each puck in a muffin cup.
5. Bake for 20 to 22 minutes, rotating the pans if necessary, or until the cookies are golden on top, browned around the edges, and slightly soft in the center; they'll firm as they cool. 
6. Transfer the pans to racks and let rest for 3 minutes, then gently pry each cookie out with the tip of a table knife and place on the racks to cool. 
7. You can serve the cookies warm, but their texture shines brighter at room temperature.

Storing: Kept in an airtight container at room temperature, the cookies will be good for at least 5 days.