Preheat Oven: Preheat your oven to 350°F (175°C). Grease and line two 9-inch round cake pans.
Mix Dry Ingredients: In a large bowl, whisk together the flour, sugar, cocoa powder, baking powder, baking soda, and salt.
Add Wet Ingredients: Add the buttermilk, vegetable oil, eggs, and vanilla extract. Beat on medium speed until well combined.
Add Boiling Water: Reduce the mixer speed to low and slowly add the boiling water. Mix until just combined; the batter will be thin.
Bake: Divide the batter evenly between the prepared pans. Bake for 30–35 minutes, or until a toothpick inserted into the center comes out clean.
Cool: Allow the cakes to cool in the pans for 10 minutes, then turn them out onto a wire rack to cool completely.
Prepare the Creamy Filling:
Beat Ingredients: In a medium bowl, beat the cream cheese until smooth. Gradually add the powdered sugar and continue beating until well combined.
Add Cream and Vanilla: Add the heavy cream and vanilla extract. Beat until the mixture is light and fluffy. Chill in the refrigerator until ready to use.
Prepare the Chocolate Ganache:
Melt Chocolate: Place the chopped chocolate in a heatproof bowl.
Heat Cream: Heat the heavy cream in a small saucepan until it begins to simmer. Pour the hot cream over the chocolate and let it sit for 2-3 minutes.
Stir: Stir the mixture until the chocolate is fully melted and smooth. If using, add the softened butter for added shine. Let the ganache cool slightly before using.
