2. Turn the dough out onto a smooth work surface, divide it in half and, working with one half at a time, shape the dough into a log that is 1 1/2 inches (4-cm) in diameter. (Cookie-dough logs have a way of ending up with hollow centers, so as you're shaping a log, flatten it once or twice and roll it up from one long side to the other, just to make certain you haven't got an air channel.) Wrap the logs in plastic wrap and chill them for at least 1 hour. (Wrapped airtight, the logs can be refrigerated for up to 3 days or frozen for 1 month.)
3. Center a rack in the oven and preheat the oven to 350 degrees F (180 degrees C). Line two baking sheets with parchment paper and keep them close at hand.
4. Working with a sharp thin-bladed knife, slice rounds that are 1/2 - inch (1-cm) thick. (Don't be upset when the cookies break, just squeeze the broken-off bit back onto the cookie.) Place the cookies on the parchment-lined sheets leaving about 1 inch (2.5 cm) of spread space between each cookie. Bake only one sheet of cookies at a time and bake each sheet for 12 minutes. The cookies will not look done, nor will they be firm, but that's just the way they should be. Transfer the baking sheet to a cooling rack and let the cookies rest, on the baking sheet, until they are only just warm or until they reach room temperature—it's your call. Repeat with the second sheet of cookies.
Keeping: The dough can be made ahead and either chilled or frozen. In fact, if you've frozen the dough, you needn't defrost it before baking—just slice the logs into cookies and bake the cookies 1 minute longer. Packed airtight, baked cookies will keep at room temperature for up to 3 days; they can be frozen for up to 1 month.
An American in Paris: In moments of over-the-topness, I've added chopped toasted pecans, plumped currants and a pinch of cinnamon to the dough and loved it. And, of course, as an American, I've been known to cheat a bit on the chocolate bits. On the sad (but fortunately seldom) occasions when my cupboard is bare of Valhrona Guanaja (Pierre's choice for these cookies and one of my favorite chocolates), I've been known to chop up ready-made chocolate chips, specifically Ghirardelli Double Chocolate Chocolate Chips.
Andrea Reusing is the creator of the restaurant Lantern in Chapel Hill, N.C., and author of the book Cooking in the Moment: A Year of Seasonal Recipes. In this installment of The Key 3, she shares with Lynne Rossetto Kasper the techniques behind three of her favorite recipes: Turnip Soup, Overnight Braised Short Ribs and Tomato Salad.