Preheat your oven to 350°F (175°C). Grease and flour three 8-inch round cake pans and line the bottoms with parchment paper for easy release.

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

In another bowl, combine the eggs, milk, oil, and vanilla extract.

Gradually add the wet ingredients to the dry ingredients, stirring until just combined. Carefully whisk in the boiling water — don’t worry if the batter looks thin; this is expected and results in a moist cake.

Divide the batter evenly among the prepared pans. Bake for 25–30 minutes, until a toothpick inserted into the center comes out clean.

Allow the cakes to cool in their pans for 10 minutes, then transfer to wire racks to cool completely.

Heat the heavy cream in a saucepan over medium heat until it begins to simmer — bubbles forming at the edges, but not boiling.

Place the chocolate pieces in a heatproof bowl. Pour the hot cream over the chocolate and let sit for 1–2 minutes. Add the butter and vanilla (if using), then stir until the mixture is smooth, glossy, and completely combined.

Let the ganache cool until it thickens but is still pourable. If it becomes too firm, warm it gently over a double boiler or in short bursts in the microwave.

Once the cake layers are fully cooled, place the first layer on your serving plate or cake stand. Spread a generous amount of ganache over the top.

Repeat with the second layer. Finish by placing the third cake layer on top.

Pour the remaining ganache over the top of the cake, allowing it to drip down the sides. Smooth the top and sides with an offset spatula for a sleek, seamless look.