First, make the cake. Preheat oven to 350F and spray three 6" round cake pans with nonstick baking spray.

In a small bowl, whisk together the ground flaxseed with the water and set aside to thicken.

In the bowl of a stand mixer, combine the flour, cocoa powder, baking powder, baking soda, salt, and sugar.

Add in the vegan butter, and beat on low until it's incorporated and has a sandy texture.

In a small bowl, whisk together the oil, flaxseed mixture, nondairy yogurt, and vanilla extract, and add them to the dry ingredients. Mix until combined.

Pour in the nondairy milk, and beat on medium-low until smooth and creamy. Add food coloring until you reach your desired color (I was generous as I was worried the color would fade with cooking!).

Divide batter evenly among the 3 pans, and bake for 30-35 minutes until cake is set in the center and a toothpick comes out clean.

When the cakes are completely cooled, you can make the frosting. In the bowl of a stand mixer, beat the shortening, vegan butter, and vanilla extract together until completely smooth and creamy. Add in the powdered sugar, 1 cup at a time, until a thick frosting forms. Add in the salt. It is normal to need to add 1-2 tablespoon of milk to get the right consistency.

Transfer about ½ of the frosting to a separate bowl, and add about 1 tablespoon of cocoa powder. Mix to combine, and add in the black food coloring until you have reached your desired color. You may need to add a little nondairy milk if it is too thick.

To the original frosting, add green food coloring until you reach your desired color.

Now, you can assemble your cake. First, trim off the tops of your cakes if they are domed or uneven.

Place one cake on your cake stand or platter, and spread some green frosting on top. Repeat with all.

Next, cover the cake with a thin layer of green frosting for the crumb coat. Cover the cake, being sure to fill in any gaps between the layers. Use a bench scraper to remove any excess (remember we want this layer to be pretty thin). Around the middle of the cake (or wherever you would like your "fault line," spread a thicker layer of the green frosting. This is where we will stick the candy eyeballs. Gently press on the eyeballs in this frosted area to create the fault line effect.

Now, chill your cake for at least 15-20 minutes so the green frosting can solidify.

For the final frosting of the cake, spoon your black frosting in a piping bag and pipe a thick layer all around the cake, avoiding the area where you have placed the eyeballs. Spread some black frosting to the top as well.

Very carefully and gently use your bench scraper to smooth out your black frosting, removing some excess and creating uneven edges at the fault line. Be gentle as you don't want to scrape so much black frosting off that the green frosting comes through.

For the top, we are going to make a swirl using our leftover green and black frosting. Place a large piece of plastic wrap on your counter, and spread the black and green frosting on it side by side (think like two long/fat ropes next to each other). Roll it up into a sausage and twirl the ends tightly. Prepare a piping bag with your desired decorating tip. Cut one of the "twirly ends" off of your frosting sausage, and carefully place it into your prepared piping bag with decorating tip. Now as you squeeze the bag, you should get both colors coming from the plastic wrap! Pipe decorations as desired on top of your cake and top with sprinkles if desired.

Serve cake immediately or refrigerate until needed - do note that I noticed the blacks of the candy eyeballs started to spread due to condensation so be careful!