Start by blooming the cocoa powder in hot coffee to awaken its rich chocolate flavor. In a medium bowl, pour the hot coffee over the sifted cocoa powder. Stir gently until well combined, then set it aside to cool slightly.

In a large mixing bowl, sift together the cocoa powder, all-purpose flour, cornstarch, and baking powder. Create a well in the center for incorporating the wet ingredients later.

In a separate bowl, beat the room-temperature eggs, milk, and dark brown sugar until smooth and creamy for about 2-3 minutes.

Gradually add the dry ingredients into the wet mixture, stirring gently to combine without overmixing.

Preheat your oven to 350°F (175°C) and prepare your cake pans. Pour the batter evenly into the prepared pans and bake for 35-40 minutes.

Once baked, let the cake layers cool in the pans for about 10 minutes before transferring them to wire racks to cool completely.

Prepare the fudge frosting by melting chopped dark chocolate and then mixing in cold butter until smooth.

Once layers are cooled, frost between them with a generous layer of fudge frosting and coat the top and sides evenly.