• Preheat the oven to 350°F (175°C). Thoroughly grease a 10- to 12-cup Bundt pan, making sure to coat all the grooves.
• In a medium bowl, whisk together the all-purpose flour, almond flour, cocoa powder, baking powder, baking soda, and salt.
• In a large mixing bowl, beat the softened butter, granulated sugar, and brown sugar for about 3–4 minutes, until lighter and fluffy.
• Add the eggs one at a time, beating well after each addition and scraping down the bowl as necessary. Mix in the vanilla.
• Add the mashed banana and mix until combined.
• Mix in the melted chocolate until evenly incorporated.
• Add the dry ingredients in three additions, alternating with the buttermilk in two additions. Begin and end with the dry ingredients and mix only until combined.
• Spoon the batter into the prepared Bundt pan and smooth the top.
• Bake for 45–55 minutes, or until a toothpick inserted into the thickest part of the cake comes out with a few moist crumbs but no wet batter.
• Let the cake cool in the pan for about 15 minutes, then carefully invert it onto a wire rack. Cool completely before adding the ganache.

Make the Chocolate Ganache

• Place the chopped chocolate in a heatproof bowl.
• Heat the heavy cream in a small saucepan until it just begins to simmer.
• Pour the hot cream over the chocolate and let stand for 2–3 minutes.
• Add a pinch of salt and stir gently until completely smooth and glossy.
• Let the ganache cool for several minutes until slightly thickened but still pourable.
• Drizzle over the completely cooled cake. Let the ganache set slightly before slicing.