Preheat the oven to 350°F
Grease & parchment line your cake pans
For the cake batter, first combine the vegetable oil with the melted vegan butter add the vanilla extract and set aside
Combine the soy milk with the vinegar and let stand for 5 minutes to thicken.
Sift all the dry ingredients including the sugar together in a large mixing bowl
Pour the wet ingredients into the dry ingredients in the bowl and whisk smooth, this will be the plant milk mixture and the butter/oil mixture
Next take out 1¼ cups of the batter and add the cocoa powder mixed with hot water to form a paste
Once the paste is cool whisk it into the batter to make the chocolate batter
Now take out an additional ¼ cup of vanilla batter and set that aside in another small bowl~ this will be for the lighter color chocolate batter
Now with half of the remaining vanilla cake batter & divide it evenly amongst your 3-7" cake pans that are greased and parchment lined
With the chocolate batter pipe the design as shown in the video tutorial in all 3 pans, you should have more chocolate batter left~ you will use this soon
Now with the reserved ¼ cup of vanilla batter in your smaller bowl, take about 3 teaspoons of the chocolate batter and mix it in~ this will give you a very light chocolate colored batter
Now pipe this lighter color batter as shown in the video tutorial
Now pipe the remaining darker chocolate batter that you still have leftover over the lighter batter as shown in the video
Now with the remaining vanilla batter gently cover over the designs in each pan with an equal amount of batter until there is no more & the designs are covered completely
And bake immediately in the preheated 350°F oven for 25 minutes, then turn the oven temperature down to 325°F to bake the rest of the way, approximately 20 minutes more or when you gently press the centers they are springy to the touch. Or do the toothpick test for moist crumbs. *Since the cake recipe is larger than normal these layers will bake slightly longer be careful not to under bake or your centers will be gooey
Cool in the pan(s) until you can safely touch them without burning yourself then turn the cake(s) out onto a cooling rack to cool the rest of the way.
Prepare the buttercream recipe according to the instructions on that page and then divide it with approximately 1½ cups for the dark chocolate decor and ½ cup for the light color decor
Once again make a cocoa paste with the hot water & cocoa powder and then add it *cooled* to the 1½ cups of buttercream
Next using just about a teaspoon of that darker BC color add it to the small ½ cup bowl of BC to make the lighter color
Build & Decorate the cake as shown in the video tutorial