SPONGE CAKE

1. Preheat Oven to 350˚F. Line bottoms of two 8″ or 9″ cake pans with parchment paper.
2. In the bowl of an electric stand mixer fitted with whisk attachment (this is the one I have), beat 6 large eggs for 1 minute on high speed. With the mixer on, gradually add 1 cup sugar and continue beating 8-10 minutes until thick and fluffy.
3. Whisk together flour, cocoa powder, espresso powder and baking powder. Sift this mixture into fluffy egg mixture one third at a time. Fold with a spatula with each addition just until incorporated. Scrape spatula from the bottom to catch any pockets of flour and stop mixing when no streaks of flour remain. Do not over-mix or you will deflate the batter.
4. Divide evenly between prepared cake pans (it helps if you have a kitchen scale to weight the pans). Bake the cake for 25-30 minutes, or until inserted toothpick comes out clean. Don’t open the oven for at least the first 20 minutes.
5. Let the cake cool for 5 minutes in the pan. Remove from pan by sliding a thin spatula around the edges then transfer to a wire rack and remove parchment backing. Then run a knife around the edges and invert onto a cooling rack. Cool completely.

MARSHMALLOW FROSTING

1. Place egg whites, sugar, and cream of tartar in a heatproof bowl. Set bowl over a saucepan filled with two inches of simmering water. Do not let it touch the water. (You can use a double boiler if you have one.)
2. Whisk constantly until sugar is dissolved and mixture has thinned out, about 4 minutes. The mixture will be thick and tacky at first, then thin out and appear frothy on top. To test that it’s ready, you can use your finger or an instant read thermometer. Lightly and quickly dip your finger (it’s very hot, be careful) and rub the mixture between your thumb and finger. You shouldn’t feel any sugar granules. If using a thermometer, the temperature should read 160°F (71°C).
3. Remove from heat. (No need to let it cool down before continuing.) Using a handheld or stand mixer fitted with a whisk attachment, beat on high speed until stiff glossy peaks form, about 5 minutes.
4. Using a handheld or stand mixer fitted with a whisk attachment in another bowl, cream together butter and sugar until light and fluffy.
5. Divide the meringue into two equal portions. Add one half to the buttercream and fold gently making sure not to deflate the peaks. Set aside.

CHOCOLATE GANACHE

1. In a heatproof bowl, add the heavy cream. Over medium heat, heat the cream. Allow to simmer until warm. Do not let it come to a boil. Pour warm cream over the chopped chocolate and stir using a spatula until the chocolate has completely melted. Set aside.

ASSEMBLY

1. Put a dollop of filling on a cake board and place the first cake layer.
2. Then spread a generous amount of marshmallow fluff (about 1 cup) over the cake layer.
3. Place the next layer and repeat until all the layers are stacked.
4. Cover the cake with the remaining marshmallow fluff to crumb coat the cake. Refrigerate it for at least 1 hour to firm up.
5. Once firmed up, frost cake all over with marshmallow buttercream.
6. Using an offset spatula touch some dollops of chocolate ganache all around the frosted cake. Move a bench scraper along the edges to create the gradient effect.
7. Pour leftover chocolate ganache in the center to create a spiral effect. Chill until set before slicing and serving.
8. Store leftovers in an airtight container  in the refrigerator for upto 5 days or at room temperature for upto 3 days.