Make the ganache: Place chopped chocolate in a medium heat-proof bowl. Heat the cream in a small saucepan over medium heat until it begins to gently simmer. Pour over chocolate, then let it sit for 2-3 minutes to gently soften the chocolate. Very slowly stir until completely combined and chocolate has melted. Set half aside at room temperature uncovered until it has thickened into a gravy-like consistency, about 30 minutes. Cover and refrigerate the rest of the ganache to use as the topping.

Preheat the oven to 350°F (177°C) and generously grease a 10-inch Bundt pan.

Mash the bananas until there’s hardly any lumps. Set mashed bananas aside.

Whisk the flour, baking powder, baking soda, cinnamon, and salt together. Set aside.

Using a handheld or stand mixer fitted with a paddle attachment, beat the butter on high speed until smooth and creamy. Add both sugars and beat on high speed until creamed together. Add the eggs and the vanilla. Beat on medium-high speed until combined, then beat in the mashed bananas.

With the mixer on low speed, add the dry ingredients in three additions alternating with the buttermilk and mixing each addition just until incorporated. The batter will be thick with some lumps.

Pour about ⅓ of the cake batter evenly into prepared pan. Drizzle half of the ganache on top. Swirl with a knife or toothpick. Evenly pour another ⅓ of the cake batter on top, followed by the rest of the ganache, then the rest of the cake batter. Swirl everything together.

Bake for 60-75 minutes or until a toothpick inserted into the cake comes out clean with just a couple lightly moist crumbs.

Once done, remove from the oven and allow to cool for 2 hours inside the pan. Then, invert the slightly cooled cake onto a wire rack or serving dish. Cool completely before topping, slicing, and serving.

Warm the ganache topping over low heat on the stove stirring constantly until thinned and drizzle-able consistency. Drizzle over cake, then slice and serve.