Preheat your oven to 350°F (175°C) and prepare two 9-inch round cake pans by greasing and flouring them.

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

In another bowl, combine eggs, buttermilk, oil, and vanilla.

Add the wet ingredients to the dry ingredients and mix until just combined.

Slowly stir in the hot brewed coffee until the batter is thin.

Divide the batter evenly between the pans and bake for 30-35 minutes, until a toothpick inserted in the center comes out clean.

Let the cakes cool for 10 minutes in the pans, then transfer to a wire rack to cool completely before assembling.

In a cold bowl, whip heavy cream and powdered sugar until stiff peaks form.

If using the optional cream cheese or mascarpone, gently fold it in until smooth.

Refrigerate the cream filling until ready to use.

Heat the heavy cream until it just begins to simmer (do not boil).

Pour it over the chopped dark chocolate and let it sit for 1-2 minutes.

Whisk until smooth, shiny, and perfectly silky.

Let it cool slightly before pouring it on the cake.

Place one cake layer on your serving plate.

Spread a generous, thick layer of chocolate cream filling on top.

Place the second cake layer gently over it.

Pour the warm ganache over the top and let it drip naturally down the sides.

Chill the cake until the ganache is set.