Preheat the oven to 350°F (175°C). Generously coat a 10- or 12-cup Bundt pan with softened butter or baking spray, making sure to reach every groove, then dust it with cocoa powder and tap out the excess.

In a large bowl, whisk together the flour, cocoa powder, sugar, baking soda, and salt until evenly combined and no cocoa clumps remain.

Add the eggs, sour cream, vegetable oil, and vanilla. Whisk until the mixture is smooth and thick, scraping the sides of the bowl as needed.

Slowly pour in the hot coffee while whisking gently. The batter will become thin, which is expected and helps create a moist cake. Do not overmix once the batter is smooth.

Pour the batter into the prepared Bundt pan and gently tap the pan on a folded kitchen towel to release large air bubbles. Bake for 45 to 55 minutes, or until a skewer inserted near the center comes out with a few moist crumbs.

Cool the cake in the pan for 15 minutes. Carefully loosen the edges with a thin spatula, invert the cake onto a wire rack, and cool completely before adding the ganache.

For the ganache, place the chopped chocolate in a heatproof bowl. Warm the cream until steaming but not boiling, pour it over the chocolate, and let it stand for 2 minutes.

Stir the chocolate and cream from the center outward until smooth, then mix in the butter. Let the ganache cool for 5 to 10 minutes so it thickens slightly, then spoon it over the cooled cake.

Let the topping set for 15 minutes. Slice with a sharp knife and serve with berries, whipped cream, or a light dusting of powdered sugar if desired.