Preheat the oven to 350° F. Spray 3 8-inch round cake pans with nonstick cooking spray and line with parchment paper. (If you don't have 3 8-inch pans, you can use 2 9-inch cake pans).
In a large bowl, add the eggs, milk, oil, vanilla, and granulated sugar and blend until smooth. In a separate bowl, whisk together the dry ingredients. Pulsing on and off, add the dry ingredients and mix until smooth. Slowly add the boiling coffee or water on low speed, being careful not to let the hot liquid splash back. After all coffee or water has been added, beat an additional 30 seconds. Batter will be thin.
Pour into prepared pans and bake for about 30-35 minutes, or until cake springs back when lightly touched or a toothpick inserted into center comes out clean. Allow to cool on wire racks for 15 minutes before removing cakes from pans to cool completely.
FOR THE FUDGE FROSTING:
In a large bowl, whisk together the powdered sugar and cocoa powder. Add the softened butter and boiling water and blend until smooth. Pour in the melted chocolate and blend to combine. The mixture will be very thin. Refrigerate it for at least 30 minutes, or until thickened up enough to spread on cake.
FOR THE GANACHE:
Place chocolate in a medium bowl. Heat heavy cream in small saucepan until hot and bubbles begin to form around edges of pan. Remove from heat and pour over chocolate. Stir mixture until chocolate melts completely. If there are still bits of chocolate not fully melted, place the bowl in the microwave for about 15 seconds at a time, stirring between, until chocolate is fully melted. Allow the ganache to cool to lukewarm before pouring over cake.
TO PUT IT ALL TOGETHER:
Place one cake layer on a cake plate or board, level it with a serrated knife if need be, and spread with about one cup of the fudge frosting. Add the second cake layer and spread with another cup of fudge frosting. Top with final layer of cake and give the whole cake a light crumb coat (coating the top and sides with a light coating of fudge frosting). Place the cake in the refrigerator to firm up and set, at least 30 minutes.
Remove the cake from the refrigerator and pour the lukewarm ganache over the cake, not all at once, but carefully adding more to the edges to allow it to run down the sides. As it pools on the cake board, use an angled spatula to pull it up and spread it onto the sides of the cake. Keep adding more around the cake at the edges and pulling it up and onto the sides until the entire cake is fully covered in ganache. You should not use all of the ganache (you may end up with half of it leftover, which can be used for other applications, poured over ice cream, or made into chocolate truffles).
Before the ganache sets, take a large amount of sprinkles and dump them onto a baking pan set underneath the cake to catch excess. Fill your hand with sprinkles and, resting your pinky and side of your hand on the cake board, slowly tip your hand towards the cake, applying gentle pressure to stick the sprinkles to the sides of the cake. Go around the whole cake, adding more sprinkles as necessary.
Refrigerate the cake until everything is completely set, about 30 minutes, before wiping away any excess sprinkles left on the board (don't throw them away--place them in a separate container to be used for another application or sprinkled over ice cream).