Preparation

Make the ganache

• Put the white chocolate in a medium heatproof bowl. In a medium saucepan over medium heat, warm the cream, espresso powder, and salt, stirring occasionally to dissolve the espresso, just until small bubbles start to form at the side of the pan, 3 to 4 minutes. Pour the cream mixture over the white chocolate, and then gently stir with a whisk until the chocolate is melted and the mixture is smooth, 1 to 2 minutes (this can also be done in a microwave). Set aside at room temperature, stirring occasionally, until cooled. Then refrigerate, stirring occasionally, until cold, about 3 hours or up to 3 days ahead. (For faster cooling, set the bowl over a larger bowl filled with an ice bath, stirring and scraping the sides frequently.)
• Pour and scrape the chilled ganache into the bowl of a stand mixer fitted with the whisk attachment. Beat the ganache on low speed to loosen, about 10 seconds. Then continue beating on low speed until slightly lighter in color and thickened, about 2 minutes. Increase the speed to medium until firm peaks form, being careful not to overbeat the ganache and scraping the bowl as needed, about 1 minute more. Cover with plastic wrap, and refrigerate until ready to assemble the cake, up to 1 day in advance.

Make the buttercream

• Put the cocoa and flour in a small saucepan. Tipping the pan to one side, add about half of the milk, and whisk until the mixture is thick and smooth. Add the remaining milk, and whisk until smooth. Set aside for at least an hour before proceeding, preferably overnight.
• 厨师,不断搅拌,煮至中低热度联合国til boiling, and then continue to boil, whisking constantly, for 1 minute. The mixture will be thick. With the pan off the heat, add the sugar, vanilla, and salt, and whisk until the sugar is dissolved.
• Put the chocolate in a heatproof medium bowl. Over the bowl with the chocolate, pour the cocoa mixture through a fine-mesh sieve to strain out any small floury bits (use a spatula to gently move the liquid through the sieve—do not press down). Scrape the underside of the sieve into the bowl, and discard the floury bits. Stir until the chocolate is melted (if necessary, microwave or set the bowl over gently simmering water). Set aside, stirring occasionally, to cool to room temperature. (For faster cooling, set the bowl over a larger bowl filled with an ice bath, stirring and scraping the sides frequently, until chilled to room temperature.)
• Put the butter in the bowl of a stand mixer fitted with the paddle attachment, and beat on medium-high speed until very smooth, about 1 minute. Add the room-temperature chocolate mixture, and beat on medium speed until smooth and well blended, about 2 minutes. Cover with plastic wrap, and keep at room temperature until ready to assemble the cake or for up to 3 hours.

Make the syrup

• In a microwave or in a small saucepan on the stove, combine the water and sugar. Cook until the sugar is dissolved, about 1 minute. Stir in the bourbon, and set aside to cool to room temperature. (For faster cooling, set the bowl over a larger bowl filled with an ice bath, stirring frequently.) Cover with plastic, and refrigerate until ready to assemble the cake or for up to 3 days.

Make the cake

• Position a rack in the center of the oven, and heat the oven to 350°F. Lightly grease the bottom and sides of a large rimmed baking sheet (13x18x1-inch), and line the bottom with parchment. Lightly grease and flour the parchment, and lightly flour the sides of the pan. Gently tap out the excess flour.
• 把面粉,烤粉和盐在一个媒介bowl, and whisk until blended. Put the eggs and egg yolk in the bowl of a stand mixer fitted with the whisk attachment (or in a large bowl using a hand-held electric mixer fitted with wire beaters). Beat on medium-high speed until pale in color, about 2 minutes. Gradually add the granulated sugar, and continue beating until very thick and tripled in volume, 2 to 3 minutes. It should be thick enough to form a ribbon of batter in the bowl when the beater is lifted. Add the oil and vanilla, and beat on medium speed until blended. Sprinkle half of the flour mixture over the eggs, and gently fold in with a large silicone spatula just until blended. Repeat with the remaining flour.
• Scrape the batter into the prepared pan, and using an offset spatula, spread evenly. Bake until the top springs back when lightly touched and the cake is just baked through but not browned, 10 to 12 minutes.
• While the cake is baking, have ready four long strips of paper towels, the confectioners’ sugar for dusting, a fine-mesh sieve, a small serrated knife, and two large wire racks.
• When the cake comes out of the oven, move the pan to a rack, and sift the confectioners’ sugar over the cake in a generous layer. Using a sawing motion, run the tip of the knife around the edges to loosen the cake from the pan. Using the same knife and a sawing motion, cut the cake crosswise into five equal strips (each 3-1/4 inches wide). You will need to trim the last strip by about 1/4 inch so that the strips are a consistent width. Arrange two overlapping paper towels on top of one single end strip, aligning the inside edges. Cover the remaining 4 cake strips completely with the remaining 3 long overlapping paper towels, and cover with a rack large enough to overhang the edges of the pan. Gripping the rack with towels and with the baking sheet sandwiched in between, flip the pan and rack to invert. Lift the pan from the cake, and carefully peel away the parchment.
• Working with one end of the single cake strip and beginning on a short side, roll up the cake and paper-towel layer together. Do this while the cake is still hot, or it will crack. Arrange seam side down on the rack. Beginning on the short sides, roll the remaining cake strips and paper towels together, hold for about 1 minute, and then unroll. Let the rolled cake strip and remaining cake strips cool completely, about 20 minutes.

Assemble the cake

• Have ready the whipped ganache, buttercream, and syrup.
• Carefully unroll the cooled curled cake strip. It will look a bit wavy and one end will be curled. Discard the paper towel. Using a pastry brush, wipe off as much of the confectioners’ sugar as possible, and put the cake strip on a new rack. Leaving behind the paper towels, move the remaining strips to the new rack, inverting them so the confectioners’ sugar side is up. Using a pastry brush, wipe off as much of the excess sugar as possible and flip them back over. Using a small sharp knife, cut a 3/4-inch bevel on the noncurly end of the curled cake strip. Repeat this beveled cut on both ends of the flat strips.
• Brush some of the syrup evenly over the curled cake strip, and spread about 1/3 cup of the ganache evenly over the strip, including into the curled edge. Gently reroll the frosted cake strip. Arrange the roll upright on parchment on a cutting board or large plate.
• Working with one cake strip at a time (brushing all the strips in advance leads to soggy, difficult-to-handle strips), brush some of the syrup evenly over the strip and gently spread about 1/2 cup of the ganache evenly over the strip, including the beveled edges.
• Positioning your hands on the short side of the strip, lift it (don’t stretch it), and wrap it around the frosted cake strip, aligning one edge with the edge of the previously wrapped strip, pressing gently but firmly so the layers hold together (that’s what I call a cake “hug”). Don’t worry if there are some small cracks. Repeat the process with the remaining strips and syrup using 1/2 cup of ganache for each strip. After wrapping the last piece, secure the end with a couple of toothpicks, if you like. If there is any remaining sugar syrup, sprinkle it over the top of the cake. Using an offset spatula, spread about 1/4 cup of the remaining ganache over the top of the cake to fill in any gaps. Refrigerate the cake for about 15 minutes to set the ganache. Cover and refrigerate any remaining ganache to use as a garnish, if you like.
• Remove the toothpicks if you’ve used them to secure the cake. Spread a thin layer of the buttercream over the sides and top of the assembled cake to seal in the crumbs. Refrigerate the cake for about 15 minutes to set the buttercream. Spread the remaining buttercream evenly over the sides and top of cake. (This is the time to use the tines of a fork to create a rustic bark pattern if you like. Also, if you want to use chopped pistachios to create the look of lichen, apply them now.)
• Refrigerate for 1 hour, then cover loosely. Chill for 1 day before serving. About 1 hour before serving, remove the cake from the refrigerator. Use a large cake spatula or lifter to move the cake to a serving platter. Discard the parchment. Top the cake with meringue mushrooms, chocolate curls, mint sprigs, silver dragées, sugared cranberries, and a dusting of confectioners’ sugar, if you like. Use a hot knife to cut the cake into wedges, wiping the knife clean before each slice.