Preheat oven to 350°F. Line the bottoms of three 6-inch (or two 8-inch) round cake pans with circles of parchment paper and spray with non-stick spray. Set aside.

Sift flour and cacao powder into a large mixing bowl. Add in coconut sugar, baking soda, and salt and whisk until combined.

Prepare your flax egg by mixing ground flaxseed with hot water. Let sit for about 10 minutes to thicken.

Add the flax egg, soy milk, olive oil, vinegar, and vanilla to the mixing bowl and whisk until just combined and smooth.

Divide batter into the prepared pans and bake for 20-25 minutes, or until a toothpick inserted into the center comes out clean. Let cool in the pans for a few minutes, then transfer to a wire rack to cool completely before frosting.

To make the frosting, add cacao wafers to a small bowl and heat in the microwave in 30 second intervals, stirring in between, until melted and smooth. Set aside for 10-15 minutes, or until cooled but still pourable.

Add softened vegan butter to a large mixing bowl and beat with a hand mixer or stand mixer for a couple minutes until creamy. Gradually beat in powdered sugar until fully incorporated, adding more if you want it sweeter. Add in cooled melted chocolate, cacao powder, yogurt, vanilla, and salt and beat until combined and smooth.

Use a serrated knife to level off the tops of the cake layers. Assemble cake with layers of frosting, plus more frosting on the sides, reserving some for decoration if desired. Place in the fridge or freezer for a few minutes to set the frosting.

Melt ⅓ cup cacao wafers and let cool slightly. Use a spoon or ziplock bag with the corner cut off to drip the melted chocolate down the sides of the cake all around the perimeter. Fill in the center with the remaining melted chocolate and spread around to fully cover the top. Sprinkle cacao sweet nibs on top. Place back in the fridge or freezer for a few minutes, until chocolate hardens.

Add remaining frosting to a piping bag and pipe swirls around the top of the cake. Serve and enjoy!