Preheat the oven to 350°F.  Line the bottom of two 8-inch (or 9-inch) round cake pans with parchment paper. Grease, and flour the sides.

In a medium bowl, whisk the hot coffee and the cocoa powder until smooth.  Set aside.

In a large mixing bowl, add the sugar, flour, baking powder, baking soda, and salt.  Whisk briefly to blend.

Add the eggs, milk, oil, vanilla, and cocoa mixture to the dry ingredients.  Mix on low speed for 30 seconds until the dry ingredients are moist.  Increase the speed to medium and beat for 1 minute.  Scrape down the sides and beat for another minute.  The batter will be thin

Pour the batter equally into the prepared pans and transfer to the center of the preheated oven.  Bake for 33 to 37 minutes for 8-inch pans and 30-35 minutes for 9-inch pans (a toothpick inserted into the center of the cakes should come out clean).

Remove the cakes from the oven and allow them to cool in the pan for 5 to 10 minutes, then run a knife around the edge of the pans to loosen the cake from the pans.  

Invert the cakes onto a cooling rack and remove the parchment paper and let the cakes cool completely before frosting.

After inverting the cakes onto the cooling rack, immediately re-invert them onto another rack and let them cool with the tops up.  They will retain more height, and the tops of the cakes won't to the cooling rack.  

Place the chopped semisweet chocolate in a large mixing bowl.

Heat the cream in a saucepan or in the microwave until it begins to steam and almost comes to a boil (but don't let it come to a boil.)  

Pour the hot cream over the chocolate. Cover the bowl, and let sit for 3-5 minutes.  Stir gently with a rubber or silicone spatula until the chocolate is completely melted and smooth.  Stir in the vanilla extract and salt, then set aside to cool to room temperature (68-73°F).

When the ganache cools to room temperature, add four tablespoons of butter and beat with an electric mixer on medium-low speed. Scrape down the sides of the bowl and add the remaining butter in two more batches. Beat well between additions.

After you add all the butter, whip the mixture on high speed for 3 to 5 minutes until fluffy. Stop the mixer to scrape down the sides and bottom several times.  

Spread a layer of frosting on one cake, then stack the other cake layer on top. Frost the top and sides of the cake, spreading as smoothly as possible.

Let the cake sit at room temperature while preparing the glaze.

Place the chopped chocolate in a bowl.

Add the cream to a small saucepan and heat just until it barely starts to boil (or place it in a bowl and heat it in the microwave). Pour the hot cream over the chocolate. 

Cover the dish and allow it to sit for 5 minutes. Stir gently with a silicone spatula until completely melted and smooth, then stir in the corn syrup and vanilla.  (Do not use a whisk, as it will create bubbles).

If there are unmelted bits of chocolate remaining, set the bowl in a larger bowl of hot tap water and continue to stir until all the chocolate has melted.

The chocolate is ready to pour while it is still slightly warm. If it cools down, it will get too thick to pour. If that happens, zap it in the microwave in 3-second bursts and stir well between bursts until it thins out again. Optionally, you can place the bowl in a larger bowl of hot water and stir the glaze until it is warm enough to pour.

Place the cake on a wire rack set over a rimmed sheet pan.  Beginning at the top center, pour the glaze in a circular pattern, using a steady stream. Gradually widen the circle to the edge of the cake and allow the glaze to flow over and down the sides of the cake.  Do not spread the glaze with a spatula, as it will mar the surface.   

Allow the cake to sit on the wire rack at room temperature until set, then transfer it to a cake plate.  

When ready to serve, dip a long, thin knife in warm water, wipe dry, and slice. Repeat the process for each slice.