Adapted from "The Essence of Chocolate: Recipes for Baking and Cooking with Fine Chocolate" by John Scharffenberger and Robert Steinberg
Makes:About 40 cookies
Rolling richly flavored cocoa cookies in white powdered sugar before baking creates a dramatic crackled look that gives these sweets—a perfect cross between brownie and cookie—a fancy appearance with virtually no effort. Use them to decorate a holiday cookie plate or for ice cream sandwiches.
Game plan: The dough freezes well—just roll it into balls (don’t dip them in the powdered sugar), place on a baking sheet, and freeze until firm. Once firm, store the dough balls in an airtight container or plastic freezer bag. To bake, remove as many balls as you need from the freezer, let thaw for 30 minutes, then roll in the powdered sugar and bake.
Place the chocolate and oil in a small saucepan over low heat, stirring occasionally until the chocolate has melted and the mixture is smooth, about 4 minutes. Remove from the heat and set aside to cool slightly.
Sift together the flour, baking powder, and salt into a medium bowl; set aside.
Place the sugar and the chocolate-oil mixture in the bowl of a stand mixer fitted with a paddle attachment and mix on medium speed until combined (the texture will be sandy), about 2 minutes. Stop the mixer and scrape down the sides of the bowl and the paddle with a rubber spatula. Return the mixer to medium speed and add the vanilla and the eggs 1 at a time, letting each completely incorporate before adding the next, about 2 1/2 minutes total. Stop the mixer and scrape down the sides of the bowl and the paddle. On low speed, add the flour mixture and mix until just incorporated, stopping once to scrape down the sides of the bowl and paddle, about 1 minute total. (The dough will be runny like batter.) Scrape down the sides of the bowl and cover with plastic wrap. Refrigerate the dough until firm, at least 2 hours or overnight.
Heat the oven to 350°F and arrange 2 racks to divide the oven into thirds. Line 2 baking sheets with silicone baking mats or parchment paper; set aside.
Place the powdered sugar on a plate or in a shallow bowl. Roll the dough into 1-inch balls (about 1 tablespoon each), drop them into the sugar, and roll until completely coated. Place 15 of the balls 2 inches apart on each of the prepared baking sheets. (Chill the remaining dough.)
Bake for 5 minutes, then rotate the sheets front to back and top to bottom and continue baking until the edges of the cookies are set but the tops are still a little soft, about 5 minutes more for soft, chewy cookies or 7 minutes more for crisp cookies. Transfer the cookies to a wire rack and cool completely. Let the baking sheets cool completely before repeating with the remaining dough (you can reuse the parchment). The cookies can be stored in an airtight container for 3 to 4 days.