Preheat the oven to 350°F (175°C). Grease and line two 8-inch round cake pans.

In a large bowl, whisk together the flour, sugar, cocoa powder, baking powder, baking soda, and salt.

Add the eggs, buttermilk, oil, and vanilla. Mix until just combined.

Slowly pour in the hot coffee while whisking until the batter is smooth. The batter will be thin — that’s normal.

Divide the batter evenly between the two prepared pans.

Bake for 30–35 minutes, or until a toothpick inserted in the center comes out with a few moist crumbs.

Let the cakes cool in the pans for 10 minutes, then turn them out onto wire racks to cool completely.

Heat the heavy cream until it begins to simmer. Pour it over the chopped dark chocolate and butter. Let sit for 2–3 minutes, then stir until smooth. Cool until spreadable.

Beat the softened butter until fluffy. Add powdered sugar and cocoa powder, then mix.

Add vanilla, a pinch of salt, and 2–3 tablespoons of cream until the frosting reaches a smooth, spreadable consistency.

Level the cake layers if needed. Place one layer on a serving plate, spread the ganache over it, then top with the second layer.

Chill briefly so the ganache sets. Finish by frosting the cake with the chocolate buttercream.

Optional: top with chocolate curls or sprinkles.