This holiday favorite takes a little extra effort, but the payoff is well worth it.
Make the Spongecake
You will need: 5 tablespoons butter/ 2/3 cup cake flour/ 1/3 cup cocoa powder/ 1/8 teaspoon baking soda/ 6 eggs/ 3/4 cup sugar/ 2 teaspoons vanilla. Preheat oven to 350 degrees. Butter a quarter sheet baking pan and line with parchment paper. Butter and flour parchment paper and pan, removing any excess flour. Set aside. Sift flour, cocoa and soda together and whisk to ensure that it is well combined. Set aside. Clarify butter by melting over low heat and skimming off any milk solids on the top. Pour amber liquid into a small bowl and keep warm until ready to use.
Make the Batter
Whisk the eggs and sugar together in a large bowl over a pot of simmering water just until the sugar is dissolved and the mixture is warmed.
Beating the eggs
Beat the warmed egg mixture on high speed until it is thick and has tripled in volume. Add vanilla and continue beating for another minute.
Add the Chocolate and Flour
Add the dry ingredients to the egg mixture a third at a time and fold in gently but enough to completely moisten the dry ingredients. Drizzle in butter after dry ingredients and fold until incorporated.
Prepping the Batter
Pour the batter over the prepared baking sheet and spread it out evenly with a spatula. Tap the pan on the counter lightly to remove any excess air bubbles. Bake for 15-18 minutes or until cake springs back when touched in the center. Err on the side of less done as overcooked will result in cracking when you begin to roll it.
Preparing the cake for rolling
Dust the top of the somewhat cooled cake with cocoa powder. Use a sharp knife to remove about an 1/8 of an inch all the way around the cake to make rolling easier. Cover the cake with waxed paper and then a damp tea towel.
Rolling the cake
Flip the cake over and remove the parchment paper. Dust the surface with cocoa powder. Beginning at one long edge gently roll the cake, waxed paper and damp towel toward the other long edge. Wrap the roll in plastic wrap and place in the refrigerator for at least 1 1/2 hours.
Making the mousse
You will need: 4 eggs separated/4 ounces semisweet chocolate/4 tablespoons unsalted butter/pinch of cream of tartar/1/2 cup heavy cream. Place chocolate and butter in a heat proof bowl over a simmering pot of water. Stir until melted and smooth. Remove from heat and add to a large mixing bowl with egg yolks. Whisk until smooth and allow to cool.
Add the Egg Whites
In another bowl, beat the egg whites and cream of tartar until stiff. Whisk a third of the egg whites into the chocolate mixture. Gently fold in the remainder a third at a time.
Add the Cream
Whip heavy cream until stiff. Gently fold whipped cream into chocolate mixture. Place mousse in refrigerator for at least 1 1/2 hours to set up.
Make the Meringue Mushrooms
You will need: 1 cup sugar/1/2 cup water/4 egg whites/1 teaspoon vanilla/1 tablespoon cocoa powder/2 ounces semisweet chocolate. Preheat oven to 225 degrees. Line a baking sheet with parchment paper. Beat egg whites on low speed to form soft peaks. Add water and sugar to small saucepan over medium low heat until sugar dissolves. Increase heat and bring syrup to a boil until it reaches hard ball stage or 248 degrees.
Add the Syrup
Increase the speed to high and carefully drizzle hot syrup in the side of the bowl of egg whites while they whip. Continue beating for about 5 minutes until egg whites are stiff and glossy. Add vanilla and beat for about 30 seconds more.
Add the Chocolate
Add the cocoa powder and gently but thoroughly fold it in, taking care not to break down the egg too much.
Make the Mushroom Pieces
Using a piping bag or plastic storage bag and a large piping tip, make button tops about 1 1/2 - 2 inches in diameter. Make stems by bringing the piping bag straight up and twisting a bit at the top to release. Dust the pieces with cocoa powder. Bake in a 225 degree oven for 2 hours.
Assemble the Mushrooms
When the meringues are baked and cooled, melt chocolate in a heat proof bowl over simmering water. Place the button tops upside down in an empty egg carton. Use a spoon to dab a bit of melted chocolate on the bottom of the button tops and hold the top of the stem in the chocolate momentarily to get it set. Place mushrooms in refrigerator to set/harden completely.
Fill the Cake Roll
Very carefully unroll the cake on a flat surface.
Fill the Cake
Evenly distribute the mousse filling from the inside rolled edge to about 1 inch from the opposite long edge. Using the towel to assist, carefully roll the cake back up with the mousse inside. Wrap the roll in plastic wrap and refrigerate for at least one hour.
Make the Ganache Frosting
You will need: 9 ounces semisweet chocolate/ 1 1/2 cups heavy cream. Heat heavy cream to just before boiling point. Pour over semisweet chocolate in a heat proof bowl. Let rest for 5 minutes and then whisk until smooth and creamy. Cool to room temperature and then beat on medium high speed until it is the consistency of frosting.
Assemble the Dessert
Remove cake roll from refrigerator and remove plastic wrap. Cut a piece from each end of the cake roll at an angle (30-45 degrees). Set aside.
Ice the Cake
Place the cake roll on the intended serving platter. Place parchment or waxed paper around edge to keep platter clean while finishing decoration. Use a spatula to add a generous amount of ganache frosting to the cake roll. Add a little extra on one end of the top and on the front side where you will attach the two pieces you cut earlier. Gently press the angled edge of the cut pieces into the icing and fill gaps with extra frosting.
Make the Details
Use a smaller tipped tool (such as a butter knife) to make ridges in the ganache frosting to replicate bark.
Add the Mushrooms
Use a little extra ganache frosting to make a base to press the bottoms of the mushrooms into.
Dust the entire cake with powdered sugar to replicate snow.
Holiday Buche de Noel
Add this holiday favorite to your dessert line up.