• Preheat the oven to 400°F. Line a sheet pan with parchment paper. 
• Whisk together the flour, cocoa, baking powder, and salt in a medium bowl and set aside. Add the egg whites to a large mixer bowl and whip on High Speed until stiff peaks form. 
• While the egg whites are whipping, combine the egg yolks, sugar, and vanilla, in a large bowl until smooth. Add the dry ingredients and whisk together until well combined.
• Now fold about 1/2 of the whipped egg whites into the chocolate mixture. Add the remaining egg whites and fold together until streaks disappear. Spread the cake batter evenly into the prepared pan and bake for 10-12 minutes.
• Remove the cake from the oven, take a knife around the edges to loosen the cake. Dust the top of the cake with a lot of powdered sugar. Cover with a tea towel. Flip the cake over and carefully remove the parchment paper. Dust with powdered sugar.
• While still hot, roll the cake in the tea towel. Set the cake aside to cool completely. 
• For the frosting Add heavy cream and egg whites to a mixing bowl with a whisk attachment. Mix for 30 seconds. then add meringue powder, cocoa powder, and powdered sugar. Whip on HIGH for 5 mins. 
• Cut the butter into chunks and while the base is whipping, begin adding them to the mixing bowl. After all the butter is incorporated add the vanilla and whip another 2 mins. Change the attachment to the paddle to knock out the air and beat for 3-5 mins. The result Is very silky and smooth. When the cake is smooth, spread the filling evenly onto the unrolled cake. Re-roll it and wrap it in plastic wrap, seam side down and refrigerate for at least an hour. 

To decorate:

• Using a serrated knife cut off 3 inches of the roll. Use the buttercream to attach it to the larger piece. Cover the outside of the roll with buttercream. Use a fork to create a wood-like texture on the cake. Decorate with sugared cranberries if you'd like. Chill until ready to serve