Step-by-Step Instructions

• Preheat your oven to 175°C / 350°F. Grease two 8-inch round cake pans and line the bottoms with parchment paper.
• In a large mixing bowl, whisk together the flour, cocoa powder, sugar, baking powder, baking soda, and salt until well combined. Sifting the cocoa powder helps remove lumps.
• Add the eggs, buttermilk, vegetable oil, and vanilla extract to the dry ingredients. Beat with an electric mixer on medium speed for about one minute until the batter is smooth and glossy.
• Carefully pour in the hot coffee. Mix gently by hand or on low speed just until the coffee is fully incorporated. The batter will be quite thin, which is normal.
• Divide the batter evenly between the prepared pans. Bake for 25 to 30 minutes, or until a toothpick inserted into the center comes out with a few moist crumbs.
• Let the cakes cool in the pans for ten minutes, then turn them out onto a wire rack to cool completely. Do not skip the cooling step, as warm layers will melt your ganache.
• While the cakes cool, make the chocolate ganache. Heat the 200 ml of heavy cream in a small saucepan over medium heat until it just begins to simmer. Do not boil.
• Place the 200 g of chopped dark chocolate in a heatproof bowl. Pour the hot cream over the chocolate and let it sit undisturbed for two minutes. Stir slowly from the center outward until completely smooth.
• Add the 30 g of butter to the warm ganache and stir until melted and shiny. Let the ganache cool at room temperature for about 15 minutes, stirring occasionally, until it thickens slightly but is still spreadable.
• Once the cake layers are completely cool, use a long serrated knife to slice each layer horizontally into two even thinner layers. You will have four thin layers total, or you can keep it to two thicker layers if preferred.
• Place one cake layer on a serving plate or cake stand. Spread a generous scoop of ganache over the top, spreading it to the edges. Stack the next layer on top and repeat until all layers are stacked.
• Cover the entire top and sides of the stacked cake with the remaining ganache. Use an offset spatula or the back of a spoon to create smooth swoops.
• Make the chocolate sauce by heating the 100 ml of heavy cream until simmering, then pouring it over the 100 g of chopped chocolate. Stir until smooth and glossy.
• Warm the chocolate sauce slightly so it pours easily, then pour it generously over the top of the ganache-covered cake. Let it drip naturally down the sides for that classic bakery look.
• Chill the finished cake in the refrigerator for 1 to 2 hours to help everything set before slicing. Serve slightly chilled or let it come to room temperature for twenty minutes first.