1 cup + 1 ½ tablespoons (87 grams) Unsweetened alkalized cocoa powder
⅜ teaspoon (1.6 grams) Baking soda
8 ounces (227 grams) Unsalted butter
2 teaspoons (6 grams) Kosher salt
¾ cup + 1 tablespoon (161 grams) Granulated sugar
For the filling: Melt the chocolate and butter together, stirring constantly. Meanwhile, bring the cream to just under a simmer.
Pour the cream over the melted chocolate and whisk to combine. Pour into a container and refrigerate for at least 4 hours, or up to 1 day, until completely chilled.
Meanwhile, for the shortbread: Place the flour in a medium bowl, sift in the cocoa and baking soda, and whisk to combine.
Place the butter in the bowl of a stand mixer fitted with the paddle attachment. Turn to medium-low speed and mix until smooth. Add the salt and mix for another 15 to 30 seconds. Add the sugar and mix for about 2 minutes, until fluffy. Scrape down the sides and bottom of the bowl.
Add the dry ingredients in 2 additions, mixing on low speed for 15 to 30 seconds after each, or until just combined, then mix until the dough begins to come together.
Mound the dough on the work surface and, using the heel of your hand or a pastry scraper, push it together into a 6-inch-square block. Wrap in plastic wrap and refrigerate for at least 1 hour, until firm. (The dough can be refrigerated for up to 2 days or frozen for up to 1 month.)
Position the racks in the upper and lower thirds of the oven and preheat the oven to 325°F (standard). Line two sheet pans with Silpats or parchment paper.
Unwrap the dough and place it between two pieces of parchment paper or plastic wrap. With a rolling pin, pound the top of the dough, working from left to right, to begin to flatten it, then turn the dough 90 degrees and repeat (this will help prevent the dough from cracking as it is rolled). Roll out to a ⅛-inch-thick sheet. If the dough has softened, slide it (in the parchment) onto the back of a sheet pan and refrigerate until firm enough to cut.
Using the fluted cutter, cut rounds from the dough. If necessary, push the trimmings together, refrigerate until firm, and reroll for a total of 16 rounds. (Any trimmings can be baked as is, cooled, and ground in the food processor to use as cookie crumbs over ice cream.) If the dough softens, return to the refrigerator until the cookies are firm enough to transfer to a sheet pan. Arrange the rounds on the sheet pans, leaving about I inch between them. (The dough can be shaped in advance; see Note.)
Bake for 15 to 17 minutes, turning the pans around halfway through baking, until the cookies are fragrant, with small cracks on the surface. (Because the cookies are so dark, it can be difficult to tell when they are done.) Set the pans on a cooling rack and cool for 5 to 10 minutes, then transfer the cookies to the rack to cool completely.
To assemble the cookies: Place the filling in the bowl of the mixer, fitted with the paddle attachment, and beat until smooth. Transfer to the pastry bag.
Turn half of the cookies over. Pipe ½ inch-long teardrops in a ring on each one, beginning ⅛ inch from the edges of the cookie, and then, working toward the center, pipe concentric rings of teardrops to cover the cookie (use 18 grams of filling per cookie). Top each with a second cookie and press gently to sandwich the cookies.
The cookies are best the day they are baked, but they can be stored in a covered container, at room temperature if unfilled, or refrigerated if filled, for up to 3 days.
Note on advance preparation: The shaped dough can be frozen on the sheet pan—wrapped in a few layers of plastic wrap—for up to 1 month. Transfer to a lined room-temperature sheet pan, and bake from frozen.
Recipe by eat. live. travel. write. at http://www.eatlivetravelwrite.com/2012/10/thomas-keller-in-toronto-and-tk-os-thomas-keller-oreos/