Preheat your oven to 350°F (175°C). Grease and flour two 9-inch round cake pans.

In a large mixing bowl, whisk together all-purpose flour, granulated sugar, unsweetened cocoa powder, baking powder, baking soda, and salt.

In a separate bowl, mix buttermilk, vegetable oil, eggs, and vanilla extract until smooth.

Gently combine the wet ingredients with the dry mixture, mixing until just incorporated.

Carefully stir in boiling water to the batter until fully combined.

Pour the batter evenly into the prepared cake pans and bake for 30-35 minutes.

After baking, let the cakes cool in their pans for about 10 minutes before transferring them to wire racks.

In a mixing bowl, beat softened unsalted butter until fluffy. Gradually mix in powdered sugar and cocoa powder.

Add milk and vanilla extract to the frosting mixture, beating until fully incorporated and smooth.

Once the cakes have cooled, frost between the layers and cover the top and sides of the cake.

Garnish with optional toppings like chocolate shavings, fresh berries, or chopped nuts. Chill for at least 30 minutes before serving.