Preheat oven to 350 degrees. Grease three, seven-inch round cake pans with a bit of coconut oil.
To a large mixing bowl add: cocoa powder, flour, baking soda, salt and coconut sugar. Stir well to combine.
Scoop two wells in the flour. In one well, add the vanilla extract. In the other well, add the vinegar. Next, pour in the water and oil. Briskly whisk by hand or beat on low with a mixer, until combined and fluffy. Do not over-beat.
Pour the batter into the three greased pans, dividing it evenly between them.
Bake the cakes at 350 degrees for 25 minutes or until fluffy and cooked through. Remove from the oven and cool for at least twenty minutes before turning upside down onto a cooling rack for the remainder of the cooling process. Tip: Placing then puffy side down when cooling helps to flatten the cakes a bit to make frosting easier.
Flash-Forward method: Instead of cooling at room temp for hours, place the cakes in the fridge – they should chill completely in about 30-60 minutes.
Just before you are ready to frost your cooled cakes, whip up your frosting. Add the shortening and vegan butter to a medium mixing bowl Whip with a beater for a minute to smooth things together. Add in the vanilla and non-dairy milk and whip to create a smooth and creamy butter mixture. Now 3/4 cup at a time, beat in the powdered sugar until everything is combined and you have a fluffy, silky, rich frosting – ready to spread! Fold in the rainbow sprinkles.
Frost your cakes. Place your first layer on a cake turntable and frost the top. Place the second cake on top of that and frost. Then finally your third cake layer on top and frost the top of that. Then smooth our the sides with the remaining frosting. Tip: Do not over-fill the center layers so you do not run out of frosting. Also: If you like A LOT of frosting, you may want to make another HALF batch of the frosting recipe. But the amount I had was just enough for my cake.
Serve same day. You can store this cake at room temp for a few hours, but any longer and you will want to place it in the fridge.