Preheat your oven to 350°F (175°C). Butter and flour three 8-inch round cake pans and line the bottoms with parchment paper. In a large bowl, whisk together the flour, sugar, cocoa powder, baking soda, baking powder, and salt. Add the buttermilk, vegetable oil, eggs, and vanilla extract. Beat on medium speed for 2 minutes until smooth. Slowly stream in the hot coffee or boiling water while mixing on low speed (the batter will be thin). Divide the batter evenly among the three pans. Bake for 28 to 32 minutes until a toothpick inserted in the center comes out clean. Cool completely.

In a large bowl, beat the softened butter for 2 minutes on medium-high speed until creamy. Gradually beat in the sifted cocoa powder until smooth. Alternately add the powdered sugar and heavy cream in small batches, mixing on low speed. Pour in the melted and cooled dark chocolate, vanilla extract, and a pinch of salt. Beat on medium-high speed for 2 more minutes until light and fluffy.

Place your first cooled cake layer onto a cake stand. Spread a thick, even layer of the chocolate fudge frosting over the top. Repeat with the second layer and more frosting. Place the final cake layer on top. Frost the top and sides of the entire cake with a thin layer of frosting (the crumb coat) and chill in the freezer for 15 minutes. Once set, apply the remaining frosting smoothly around the entire cake. Chill the cake again for 30 minutes.

Combine the chocolate chips and heavy cream in a microwave-safe bowl. Microwave in 20-second bursts, stirring in between, until the chocolate is completely melted and smooth. Let the ganache cool for about 10 minutes until it is warm and slightly thickened but still pourable.

Pour the warm ganache onto the center of the chilled cake. Gently push the ganache over the edges so it runs down the sides in clean drips. While the glaze is still wet, pile the chopped dark chocolate chunks and chocolate shavings directly in the center of the top of the cake. Keep in the refrigerator until ready to slice and serve!