Prepare the Cake Layers:

• Preheat the Oven: Set your oven to 350°F (175°C). Grease and flour two 9-inch round cake pans or line them with parchment paper.
• Mix Dry Ingredients: In a medium bowl, whisk together the flour, cocoa powder, baking powder, baking soda, and salt. Set aside.
• Cream Butter and Sugar: In a large mixing bowl, beat the softened butter and granulated sugar until light and fluffy, about 3-4 minutes.
• Incorporate Eggs and Vanilla: Add the eggs one at a time, mixing well after each addition. Then, mix in the vanilla extract.
• Combine Dry Ingredients and Buttermilk: Add the dry ingredients to the butter-sugar-egg mixture in three additions, alternating with the buttermilk in two additions. Start and end with the dry ingredients. Mix on low speed after each addition until just combined.
• Add Hot Coffee: Stir in the hot coffee. The batter will be thin but ensures a moist, fudgy texture.
• Bake the Cakes: Divide the batter evenly between the prepared pans. Bake for 39-44 minutes, or until a toothpick inserted into the center comes out clean. Let the cakes cool in the pans for 10 minutes, then transfer them to wire racks to cool completely.

Prepare the Dark Chocolate Buttercream:

• Melt the Chocolate: In a heatproof bowl, melt the dark chocolate using a microwave or double boiler. Let it cool slightly.
• Beat Butter and Add Cocoa Powder: In a large bowl, beat the softened butter until creamy. Add the cocoa powder and mix until well combined.
• Incorporate Melted Chocolate: Add the melted chocolate to the butter-cocoa mixture and beat until smooth.
• Add Powdered Sugar: Gradually add the powdered sugar, one cup at a time, mixing on low speed and increasing to medium speed until the mixture becomes fluffy.
• Adjust Consistency: Add heavy cream one tablespoon at a time until you reach a spreadable consistency.

Assemble the Cake:

• Level the Cakes: If the cakes have domed on top, use a serrated knife to level them for even stacking.
• Apply Buttercream: Place the first cake layer on a serving plate or cake board. Spread a layer of dark chocolate buttercream over the top. Place the second cake layer on top and apply a thin crumb coat of buttercream over the entire cake. Refrigerate for at least 30 minutes to set the crumb coat.
• Final Layer of Buttercream: After chilling, apply a final, thicker layer of buttercream over the cake, smoothing the sides and top.

Prepare the Dark Chocolate Ganache:

• Heat the Cream: In a small saucepan, heat the heavy cream over medium heat until it begins to simmer (do not let it boil).
• Combine with Chocolate: Pour the hot cream over the chopped dark chocolate in a heatproof bowl. Let it sit for 2-3 minutes, then stir until smooth and glossy.
• Drip the Ganache: Allow the ganache to cool slightly before drizzling it over the top of the cake. Use a spoon to create drips along the edges, then pour the remaining ganache over the center of the cake.