Preheat oven to 350 degrees Fahrenheit and spray a 9 x 9 inch pan with non-stick cooking spray.  Mix all ingredients together in a medium bowl until there are no lumps.  Pour into the pan and bake for 20-25 minutes. 

While the cake is baking, melt butter in a small sauce pan on medium heat with sugar and cocoa powder.  Mix well and add evaporated milk.  

Bring to boil and stir constantly for 7 minutes.  Take off the heat and add vanilla.

When the cake has cooled for 10-15 minutes, remove from pan and poke holes all around the top with a fork.  Drizzle the hot fudge sauce on top spreading with the back of a spoon creating a thin layer of fudge.  It is okay if some of it spills over the sides.  Reserve about 2 tablespoons for later.  Allow to cool.

Separate eggs - put yolks in a medium sauce pan and whites in a medium bowl.  Place coffee grounds in a glass measuring cup with the water.  Heat in microwave for 30 seconds.  (You can use more coffee - up to 1 Tablespoon if you want a stronger coffee flavor - the coffee enhances the chocolate flavor.)  Place the coffee mixture in a small sauce pan with the sugar.  Mix together over medium heat and bring it to a boil to make a simple syrup.

Whisk yolks until they are pale yellow.  Slowly add the coffee syrup, whisking the entire time.  Once the two are incorporated whisk the mixture over a pan of simmering hot water.  Whisk until the mixture is thickened and ribbons form when you pull a spoon up and drip the mixture down.  It will take a long time so be patient.  I use my immersion blender with the whisk attachment.   

Place the mixture in a bowl of a stand mixer and mix on high until it has thickened and become fluffier.  

Melt the chocolate in a bowl in the microwave or over a double boiler.  Mix in the butter until it is smooth.  

Pour the chocolate mixture into the egg yolk and coffee syrup mixture and fold in.  

Whisk the egg whites until it just begins to foam, add the 1 tablespoon of sugar.  Continue mixing until stiff peaks form and it can hold its shape.  I use the immersion blender with whisk attachment for this as well.

Fold the egg whites into the chocolate mixture.  Chill for about 4 hours.

Mix all ingredients together in a medium bowl with a hand mixture until it is firm.  Chill.

To assemble, spread the chilled mousse over the hot fudge.  It will be about 1/2 inch thick.  Next, spread the whip cream over the mousse.  Place the remaining hot fudge in a plastic zip-lock bag and cut a tiny bit of the corner off to drizzle over the whip cream. (You may need to warm the hot fudge in the microwave for about 10 seconds.)  Chill again or enjoy right away!