For the cake:
2 cups graham cracker crumbs
2 tsp. baking powder
¼ tsp. salt
3 large eggs, separated
8 tbsp. unsalted butter, at room temperature
1 cup sugar
1 tsp. vanilla extract
1 cup milk
For the filling:
For the milk chocolate glaze:
8 oz. milk chocolate, finely chopped
¼ cup heavy cream
2 tbsp. unsalted butter cut into 4 pieces, at room temperature
2 tbsp. light corn syrup
3 tbsp. unsalted butter, softened
½ cup marshmallow fluff
¾ cup confectioners’ sugar, sifted
2 tsp. heavy cream or milk
Small rectangles of graham cracker and milk chocolate, for garnish
To make the cake, preheat the oven to 375° F. Line the bottom of two 9-inch round cake pans with parchment or wax paper. Grease and flour the sides of the pans; set aside. In a medium bowl, combine the graham cracker crumbs, baking powder and salt; stir together and set aside.
In the bowl of an electric mixer fitted with the whisk attachment, beat the egg whites on medium-high speed until soft peaks form. Transfer to a separate bowl and set aside. Replace the mixer bowl and fit with the paddle attachment. Cream together the butter and sugar and beat on medium speed until light and fluffy, about 2 minutes. Mix in the egg yolks until well combined. Stir in the vanilla extract.
Add in the dry ingredients alternately with the milk on low speed, beginning and ending with the dry ingredients and mixing just until incorporated. Using a rubber spatula, fold in about a third of the egg whites to lighten the batter. Gently fold in the remaining egg whites until completely incorporated.
Divide the batter evenly between the prepared pans. Bake the cakes for about 20 minutes or until a toothpick inserted in the center comes out clean. Allow the cakes to cool in the pans for about 5-10 minutes, then invert onto a wire rack, remove the parchment paper and let cool completely.
Once the cake has cooled completely, transfer one of the cake layers to a cardboard cake circle and place on a serving platter. Carefully spread a layer of marshmallow fluff over the cake, not quite reaching the edges. Top with the remaining cake layer and refrigerate for about 1 hour.
To make the milk chocolate glaze, combine the chocolate, cream, butter and corn syrup in a heatproof bowl set over simmering water. Heat until the chocolate has melted, then whisk the ingredients together until completely smooth. Pour glaze over the top of the chilled cake, allowing it to run down the sides in some places. Return to the refrigerator to chill until set.
To make the marshmallow frosting for decoration, combine the butter and marshmallow fluff in the bowl of an electric mixer. Beat on medium speed until smooth. Beat in the confectioners’ sugar until well combined. Stir in the cream or milk to smooth the frosting out a bit, adding a tiny bit more liquid if necessary.
Transfer the frosting to a pastry bag. Pipe dollops of frosting around the edges of the chilled cake and decorate with segments of graham cracker and milk chocolate. Store in the refrigerator until ready to serve. Allow to sit at room temperature about 20 minutes before serving.