Yule Log Cake

Instructions

To make the cake:

1. Line a 10×15-inch jelly roll pan with parchment paper and spray with nonstick cooking spray.
2. Set a rack in the middle level of the oven and preheat to 350 degrees.
3. Fill a medium saucepan halfway with water and bring it to a boil over medium heat. Lower the water to a simmer.
4. Whisk the eggs, yolks, salt and sugar in the bowl of a heavy-duty mixer. Place over the pan of simmering water and whisk gently until the mixture is just lukewarm, about 100 degrees. (Use your finger to test it.)
5. Place on mixer with whisk attachment and whip on high, but not highest, speed until the egg mixture is cool (touch the outside of the bowl to tell) and has increased greatly in volume.
6. While the eggs are whipping stir together the flour, cornstarch and cocoa.
7. Take the bowl off the mixer and sift 1/3 of the flour mixture over the beaten eggs. Use a rubber spatula to fold in the flour mixture, making sure to scrape all the way to the bottom of the bowl on every pass through the batter to prevent the flour mixture from accumulating there. Repeat with the next 1/3 of the flour mixture and finally with the remaining flour mixture.
8. Scrape the batter into the prepared pan and smooth the top.
9. Bake the genoise in the preheated oven for 10 to 12 minutes, or until well risen and firm. Do not let the cake bake dry.
10. Use a small paring knife to loosen the cake from the side of the pan. Invert the cake to a rack, then immediately re-invert to another rack so that the cake cools on the paper.

To make the caramel buttercream:

1. Whisk egg whites and sugar in a heatproof bowl over a pan of simmering water until sugar is dissolved and the mixture is warm, about 2-3 minutes.
2. Beat mixture with electric beaters until stiff. Add butter in tablespoonfuls until combined.
3. Add vanilla and beat on low speed until it thickens up, about 5-10 minutes.

To make the chocolate buttercream:

1. Melt the chocolate. You can do this on half power in the microwave or in a double boiler. Don’t overheat.
2. When melted, set aside to cool.
3. Combine the egg whites and sugar in the bowl of an electric mixer and whisk gently over simmering water until the sugar is dissolved and the egg whites are hot.
4. Whip on medium speed until cold.
5. Beat in softened butter and continue beating until the buttercream is smooth.
6. Stir in the chocolate that has cooled slightly.

To make the meringue mushrooms:

1. Preheat the oven to 225 degrees F. Line 2 baking sheets with parchment. Have ready a pastry bag fitted with a small (no. 6) plain tip. In a bowl, using a mixer on medium-low speed, beat together the egg whites and cream of tartar until very foamy. Slowly add the granulated sugar while beating. Increase the speed to high and beat until soft peaks form when the beaters are lifted. Continue until the whites hold stiff, shiny peaks. Sift the icing sugar over the whites and, using a rubber spatula, fold in until well blended.
2. Scoop the mixture into the bag. On one baking sheet, pipe 48 stems, each ½ inch (12 mm.) wide at the base and tapering off to a point at the top, ¾ inch (2 cm.) tall, and spaced about ½ inch (12 mm.) apart. On the other sheet, pipe 48 mounds for the tops, each about 1-1/4 inches (3 cm.) wide and ¾ inch (2 cm.) high, also spaced ½ inch (12 mm.) apart. With a damp fingertip, gently smooth any pointy tips. Dust with cocoa. Reserve the remaining meringue.
3. Bake until dry and firm enough to lift off the paper, 50-55 minutes. Set the pans on the counter and turn the mounds flat side up. With the tip of a knife, carefully make a small hole in the flat side of each mound. Pipe small dabs of the remaining meringue into the holes and insert the stems tip first. Return to the oven until completely dry, about 15 minutes longer. Let cool completely on the sheets.

To make the sugared cranberries:

1. In a small saucepan, combine granulated sugar and water over low heat. Stir mixture until all of the sugar dissolves. Bring to a simmer; remove from heat. If the mixture boils, cool slightly, if too hot the cranberries may burst. Stir in cranberries and pour mixture into a bowl. Cover with saran wrap and refrigerate overnight.
2. Drain cranberries in a colander over a bow. Place superfine sugar in a shallow dish. Add the cranberries, rolling to coat with sugar. Spread sugared cranberries in a single layer on a baking sheet; let stand at room temperature 1 hour or until dry.

To assemble:

1. Run a sharp knife around the edges of the genoise to loosen it from the pan.
2. Turn the genoise layer over (unmolding it from the sheet pan onto a flat surface) and peel away the paper.
3. Carefully invert your genoise onto a fresh piece of parchment paper.
4. Spread with the caramel buttercream.
5. Use the parchment paper to help you roll the cake into a tight cylinder.
6. Transfer back to the baking sheet and refrigerate for several hours.
7. Unwrap the cake. Trim the ends on the diagonal, starting the cuts about 2 inches away from each end.
8. Position the larger cut piece on each log about 2/3 across the top.
9. Cover the log with the reserved buttercream, making sure to curve around the protruding stump.
10. Streak the buttercream with a fork or decorating comb to resemble bark.
11. Transfer the log to a platter and decorate with your mushrooms and sugared cranberries.