Preheat your oven to 350°F (175°C) and prepare two 8-inch round cake pans by buttering them and lining with parchment paper.

In a large mixing bowl, whisk together the all-purpose flour, white sugar, cocoa powder, baking soda, baking powder, and a pinch of salt.

In a separate bowl, whisk together the buttermilk, vegetable oil, eggs, and vanilla extract. Gradually stir in the brewed coffee.

Pour the wet mixture into the bowl of dry ingredients and stir gently until smooth. Add the hot brewed coffee to thin the batter.

Reserve about one cup of the batter for cupcakes to create crumbs for decoration.

Divide the remaining batter between the two prepared cake pans and bake for about 35 minutes, or until a toothpick comes out clean.

Bake the reserved cupcake batter in liners for approximately 15 minutes.

Allow the cake layers to cool for about 10 minutes in the pans before transferring them to a wire rack.

Prepare the chocolate pudding filling by whisking cocoa powder into boiling water, then add sugar, bittersweet chocolate, and salt until smooth.

Thicken the pudding by mixing cornstarch with cold water, whisking for one minute over medium heat until thickened.

Melt the remaining butter and semisweet chocolate together for the frosting, stirring in hot water, corn syrup, and vanilla until glossy.

Pulse the cooled cupcakes in a food processor to create fine crumbs for decoration.

Assemble the cake by layering one cake layer with chocolate pudding filling, then the second layer on top.

Frost the sides with remaining pudding and press cupcake crumbs onto the sides.

Chill the cake in the refrigerator until ready to serve for enhanced flavor.