Preheat your oven to 350°F (175°C) and prepare two 9-inch round cake pans by greasing with butter and dusting with flour.

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

In a separate bowl, whisk together the buttermilk, vegetable oil, eggs, and vanilla extract until smooth.

Pour the wet ingredients into the dry ingredients and mix gently until just combined.

Gradually stir in the boiling water until the batter is smooth.

Divide the batter evenly between the prepared cake pans and bake for 30-35 minutes until a toothpick comes out clean.

Cool the cakes in the pans for 10 minutes before transferring to a wire rack to cool completely.

In a mixing bowl, beat the softened butter until fluffy, then gradually mix in the powdered sugar and cocoa powder.

Frost the top and sides of the cooled cakes with the prepared frosting.

Garnish with chocolate shavings, fresh berries, or chopped nuts and chill in the fridge for at least 30 minutes before serving.