Cake:
1 cup flour
2 tsp. baking powder
1 c. sugar
1/2 c. cocoa powder
4 oz. Special Dark Chocolate Chips, melted and cooled
8 eggs
1/2 c. mayonnaise
2 tsp. vanilla extract
Filling & Frosting:
8 egg whites
2 c. sugar
1 tbsp. vanilla bean paste
3 c. (6 sticks) unsalted butter (room temperature)
8 oz. Special Dark Chocolate Chips, melted & cooled (for bark)
1/4 c. malted milk powder (for filling)
5 oz. box Whoppers, crushed (for filling)
Preheat the oven to 350 degrees and butter two half-sheet pans, then line the pans the long way with parchment paper leaving an overhang on each end. Butter the parchment as well - set aside.
In the bowl of an electric mixer fitted with the paddle attachment add sugar and mayonnaise, beating for one minute to dissolve sugar. Add eggs, one at a time until each one is incorporated - then add vanilla and melted chocolate. Add flour, cocoa and baking powder - turn mixer on low speed until combined, scraping bowl if necessary. Divide batter evenly between the two half-sheet pans and bake for 15-18 minutes. Remove from oven and allow to cool completely. Place parchment on top of each cake and place a second half-sheet pan over, then flip cake out. Peel off parchment liner when ready to frost.
To make the filling/frosting, in the bowl of your mixer place egg whites and sugar. Set the bowl over a saucepan of simmering water and whisk by hand until the sugar is dissolved. I test this by placing my forefinger and thumb into the mixture and feeling it between them for sugar granules. When you notice they are gone are barely there, remove from heat and place into mixer fitted with whisk attachment. Add the vanilla bean paste and beat on high speed until the egg whites become firm, roughly five minutes. With the machine still running, drop the room temperature butter by tablespoons into the egg whites, slowly incorporating the butter in. Beat the mixture until it comes together, it will completely change the look and texture - looking like buttercream icing.
Scoop out two cups of the icing into a small bowl and whisk in the 4 oz. melted-cooled chocolate by hand, cover and set aside.
Add malted milk powder and crushed Whoppers (which I crushed in the food processor) to the remaining buttercream and mix to combine well. Remove from mixer and divide evenly between two cake layers, spreading the malted icing over them. Cut cakes in half lengthwise and gently roll one up over itself the long way. The cake may crack/break - this is okay. Take the first rolled cake and attach it to the end of the other half, rolling that cake up and around the first roll. Continue to do this until you have rolled all four layers together. Place cake flat side up onto serving plate, then using the chocolate buttercream frost the outside of the trunk - frosting it from the bottom up to create a bark effect.
Cover with plastic wrap and chill for at least six hours, or overnight if possible. Garnish it with fresh cranberries, sugared rosemary and meringue mushrooms.
