Preheat the oven to 180°C. Grease and line a 20 cm round cake tin with parchment paper.
In a large bowl, mix 200 grams of all-purpose flour, 200 grams of sugar, 75 grams of cocoa powder, 1 1/2 teaspoons of baking soda, and 1 1/2 teaspoons of baking powder.
Add 240 ml of buttermilk, 120 ml of vegetable oil, 2 large eggs, and 2 teaspoons of vanilla extract to the dry ingredients. Mix well until combined.
Slowly pour in 240 ml of boiling water and mix until the batter is smooth. Pour the batter into the prepared cake tin.
Bake for 30-35 minutes or until a toothpick inserted in the center comes out clean. Allow the cake to cool in the tin for 10 minutes, then transfer to a wire rack to cool completely.
To prepare the chocolate truffle frosting, heat 480 ml of heavy cream in a saucepan until it starts to simmer. Remove from heat and add 600 grams of chopped dark chocolate. Let it sit for 5 minutes, then stir until smooth and glossy.
Allow the chocolate truffle frosting to cool at room temperature, stirring occasionally, until it reaches a spreadable consistency.
Once the cake is completely cooled, slice it horizontally into two equal layers. Spread a generous layer of chocolate truffle frosting on the bottom layer, then place the second layer on top. Cover the entire cake with the remaining frosting, creating a smooth and even layer.
Decorate the Chocolate Truffle Pastry with chocolate shavings or curls, and refrigerate for at least 1 hour before serving.