Preheat the oven to 350°F (180°C). Spray two 9-inch* baking pans with non-stick spray and line the bottoms with a circle of parchment paper. Set aside.
Sift the flour and the cocoa powder into a mixing bowl. Add the sugar, baking soda and salt.
Prepare the vegan buttermilk by adding 1 ½ Tablespoons lemon juice to a measuring jug and then adding soy milk up to the 1 ½ cup (360ml) line. Leave it for a minute to curdle.
Add the vegan buttermilk, vanilla, oil, vinegar and applesauce and mix in. Use a hand whisk briefly to remove any large lumps. Don't overmix.
Divide the batter between the two prepared cake pans.
Bake for 30 minutes or until a toothpick inserted into the center of one of the cakes comes out clean.
Let the cake layers cool for a few minutes and then remove them from the cake pans and transfer to wire cooling racks to cool completely before frosting.
Prepare your frosting by adding your vegan butter, powdered sugar, cocoa powder, salt, vanilla and 1 Tablespoon soy milk to the bowl your stand mixer. Start off at slow speed and gradually increase speed until your frosting is thick and smooth. If it's too thick, add the remaining soy milk until it reaches a spreadable consistency.
Frost the cooled cakes and decorate with chocolate shavings.