Preheat the oven to 350 degrees F. Line cupcake pans with cupcake liners (for a total of 44 cupcakes).
For the banana cake batter: In a large bowl, mix together the sugar, butter, vanilla and eggs. In another bowl, sift together the flour, baking powder, baking soda and salt. Add the flour mixture to the butter mixture. Add the bananas and buttermilk and beat together well.
For the dark chocolate cake batter: Put the cocoa in a medium heatproof bowl, pour 2 cups boiling water over it and whisk until smooth. Let the mixture cool.
Sift together the flour, baking soda, baking powder and salt in a medium bowl and set aside.
In a large bowl, cream the butter and sugar together until light and fluffy. Beat in the eggs one at time, and then stir in the vanilla. Add the flour mixture alternately with the cocoa mixture.
Fill the cupcake liners one-third full with the banana cake batter. Add the dark chocolate cake batter on top, filling the liners about two-thirds full. Bake until an inserted toothpick comes out clean, 16 to 19 minutes. Allow the cupcakes to cool completely before frosting.
For the ganache: Melt the chocolate chips and heavy cream in a double boiler, stirring the entire time. (Be careful not to get steam or water into your chocolate mixture, as it will seize.) Stir until completely melted and smooth. Add additional cream as needed a tablespoon at a time.
For the buttercream: In a large bowl, whip the butter until light and fluffy. Gradually add the sweetened condensed milk, vanilla, banana bakery emulsion and bananas. Whip until smooth and creamy.
Pipe the frosting onto the cupcakes. Drizzle with the chocolate ganache using a squeeze bottle or spoon.
This recipe was created by a contestant during a cooking competition. It has not been tested for home use.