2. Place all dry ingredients (flour, cocoa powder, baking soda,
baking powder, sugars and salt) into the bowl of a stand mixer. Mix
until well combined. In a medium bowl, whisk eggs, oil, buttermilk,
and vanilla. Very slowly pour in hot hot chocolate while whisking
Place one layer of cake onto a cake stand or serving plate. Pipe a
dam around the edge with the chocolate frosting and fill with
approximately 1 cup of marshmallow fluff. Spread evenly.
Place remaining layer on top and crumb coat the cake. Refrigerate
for 20 minutes.
Frost the cake with the chocolate frosting, smoothing the sides and
top. Place back in the refrigerator for 20 minutes to set.
Pipe a scallop pattern (using a large round piping tip and a small
offset spatula, following this technique) on top and bottom edges
using the remaining marshmallow fluff. Top with chocolate
shavings if desired.