Instructions

For the Black Chocolate Cake

1. Preheat the oven to 360 degrees F. Spray four 6-inch round cake pans with nonstick spray. (You can also use three 8-inch pans). Line the bottom of each pan with parchment paper, then spray the pans again.
2. Combine the flour, sugar, cocoa, baking soda, baking powder, and salt into the bowl of an electric mixer fitted with a paddle attachment and mix on low speed until combined.
3. In another bowl, combine the buttermilk, oil, eggs, water, and vanilla.
4. With the mixer on low speed, slowly add the wet ingredients to the dry. Mix until just incorporated. Scrape down the sides of the bowl. Add the food gel and mix for another 20 seconds. 
5. Pour the batter into the prepared pans (about 11 to 12 in each of the 6-inch pans or 15 to 16 ounces in each of the 8-inch pans) and bake for 16-18 minutes.  
6. Cool in the pans for 10 minutes, then turn them out onto a cooling rack and cool completely.
7. Level each cake layer as needed and then wrap in plastic wrap and chill until ready to use. 

For the Black Fudge Frosting

1. In a bowl of stand mixer fitted with paddle attachment beat the butter on medium-high speed until light and fluffy, about two minutes.
2. In a small mixing bowl, combine the hot water and cocoa powder. The mixture will be thick like a paste. Set aside.
3. In a microwave safe bowl, heat the chocolate chips until melted and smooth. Let cool slightly, but not all the way to room temperature.
4. Reduce the mixer's speed to medium and slowly stream in the melted chocolate, making sure to scrape down the sides of the bowl occasionally so the chocolate doesn't harden around the sides of the bowl.
5. Add the cocoa paste (cocoa and water mixture), followed the vanilla and salt.  Beat until incorporated, about 1 minute.
6. Decrease the speed to low and gradually add the powdered sugar. Once the powdered sugar is incorporated, add the black food gel and then beat for about two minutes. The color will likely be grey. Don't worry. Your next job is to be patient!
7. Let the frosting sit for at least a couple of hours (even a full day is great) because the color will take awhile to process and it's best to let it sit rather than adding more and more coloring right away.
8. If you've let the frosting rest for plenty of time and it's still not black, add one more teaspoon of black food gel and let it rest a bit more.
9. If your frosting is too soft, cover it with plastic wrap and let it chill in the refrigerator a bit.

For the Colored Vanilla Buttercream

1. In a bowl of stand mixer fitted with paddle attachment beat the butter on medium speed until light and fluffy, about five minutes.
2. With the mixer on low speed, slowly add the powdered sugar, followed by the vanilla, salt and heavy whipping cream. Turn the mixer to medium-high and beat the frosting for about five minutes, until lighter in color and texture.
3. Divide the frosting in small mixing bowls and tint the frosting  your desired colors

Assembly

1. Place a cake board onto your turntable. Apply a small dollop of frosting onto the cake board and smooth it out with an offset icing spatula. Place the first cake layer on top of the thin layer of frosting which will act like glue to hold the cake in place.
2. Evenly spread your first color of frosting on the cake layer, making sure to get eye level with the cake to ensure you're layer of frosting is even.
3. Continue to stack and frost the layers until the last cake layer, which you'll place top side (crumb side) down on the last layer of colored frosting.
4. Apply a thin coat of black frosting around the entire cake, making sure to cover the entire cake from top to bottom. Freeze the cake for 10 to 15 minutes to lock in the crumbs.
5. When the frosting is set and the crumbs are locked in place, continue to frost the cake with the remaining frosting.