Preheat oven to 350 degrees. Line cupcake pan with baking cups or use large nut cups. Set aside.
In a mixing bowl, whisk together the flour, sugar, baking soda, and salt. Add the eggs and oil and stir just until the dry ingredients are moistened; do not beat. Stir in the banana, buttermilk and vanilla. Fold in roughly chopped dark chocolate.
Divide the batter among the cupcake liners and bake for 17 to 23 minutes, or until a wooden pick inserted in the center comes out clean.
Allow cupcakes to cool COMPLETELY before frosting with ganache (recipe below).
To make ganache, in a double boiler over simmering water, cook the last three ingredients--heavy cream, chocolate chips, and instant coffee--until smooth and warm, stirring occasionally.