准备

混合面团：

• Sift together the flour, salt, and baking soda. In the bowl of a stand mixer fitted with the paddle attachment, cream the butter on medium-low speed until smooth, about 2 min. Add the sugar in a steady stream and mix for another 2 min. Add the egg and vanilla and mix until well combined, scraping the bowl as needed. Reduce the speed to low and add the dry ingredients in two additions, mixing just until combined. Remove 2 cups less 2 Tbs. of the dough and set aside.
• Dissolve the espresso powder in the boiling water and set aside briefly to cool. Then mix the espresso and cocoa powder into the remaining dough. Reduce the mixer speed to low, add the warm melted chocolate and mix just until thoroughly combined.

滚动风车日志：

• Portion each flavor of dough into three equal pieces. (For accuracy, use a scale.) Shape each piece into a 5×5-inch square on a piece of plastic wrap and wrap well. The chocolate will be thicker than the vanilla. Refrigerate the dough for 30 min. (If the dough becomes too hard, let it stand at room temperature for a few minutes before rolling).
• 当面团凉爽时，撕下十二个12英寸的蜡纸。将每片面团滚动到两张蜡纸之间的7×7英寸正方形中。在不卸下蜡纸的情况下，将面团的正方形在烤盘上层上，然后冷藏10至15分钟。准备好三张15英寸的保鲜膜。
• To shape the cookies, remove one square of the vanilla dough and one square of the chocolate dough from the refrigerator and peel off the top sheet of waxed paper from each. Invert the chocolate square over the vanilla square (or vanilla can go on top of chocolate; try some of each for variety), taking care to align the two layers as evenly as possible. Using your rolling pin, gently roll over the dough to seal the layers together. Peel off the top layer of waxed paper.
• 从最接近您的面团的边缘开始，用指尖小心地将面团的边缘卷曲，因此在风车的中心看不到空间。
• 用蜡纸作为辅助，继续将面团滚成紧密的圆柱体。圆柱体形成后，将其来回滚动，以稍微拉长并将其压实。将日志传输到塑料包裹中，以最接近您的长边缘为中心。紧紧滚动，将塑料的末端牢固地拧紧以密封。双手在原木的任一端，将牢固地推向中心以压缩面团。它应该长约9英寸，厚1-1/2英寸。重复剩余的面团。冷藏原木，直到足够牢固地切成薄片，约3小时或冷冻长达三个月。

Bake the cookies:

• Position racks in the upper and lower thirds of the oven. Heat the oven to 350°F. Line two rimmed baking sheets with parchment. Working with one log at a time, use a sharp, thin-bladed knife to slice the dough into 3/16-inch rounds. Set the rounds about 1 inch apart on the prepared pans and bake until the tops of the cookies feel set, 12 to 14 min. (don’t let the edges become too brown). To ensure even browning, rotate the sheets as needed during baking. Let the baked cookies stand for 1 minute on the pan. While they’re still warm, use a thin metal spatula to transfer them to racks. When cool, store between sheets of waxed paper in an airtight container for up to two weeks, or freeze for up to three months.