Step 1: Prep the Cake Batter

1. Preheat oven to 325°F. Grease two 8-inch round cake pans and line with parchment paper.
2. In a bowl, whisk together flour, baking powder, baking soda, and salt.
3. Melt butter in a saucepan, then stir in cocoa, granulated sugar, and brown sugar.
4. Remove from heat and mix in buttermilk, coffee, and vanilla.
5. Whisk in eggs one at a time.
6. Stir in the flour mixture until just combined.

Step 2: Bake the Cake

1. Pour batter evenly into prepared pans.
2. Bake for 35-40 minutes or until a toothpick inserted in the center comes out clean.
3. Cool in pans for 10 minutes, then transfer to wire racks to cool completely.

Step 3: Prepare the Chocolate Pudding

1. In a saucepan, whisk together sugar, cornstarch, and salt.
2. Gradually add milk, stirring constantly.
3. Cook over medium heat until thickened.
4. Remove from heat and stir in chopped chocolate and vanilla.
5. Refrigerate until cold.

Step 4: Make the Frosting

1. Melt chocolate and butter in a double boiler.
2. Remove from heat and whisk in hot water, corn syrup, and vanilla.
3. Refrigerate for 25-30 minutes or until spreadable.

Step 5: Assemble the Cake

1. Slice each cake horizontally to create four layers.
2. Set one layer aside to be crumbled later.
3. Place one cake layer on a serving plate and spread half the pudding on top.
4. Repeat with the second layer and remaining pudding.
5. Top with the third cake layer.

Step 6: Frost and Finish

1. Frost the entire cake with chocolate frosting.
2. Crumble the reserved cake layer and press crumbs onto the top and sides of the cake.
3. Refrigerate before serving.