Whisk all dry ingredients for the cake batter (flour, both types of sugar, salt, baking powder and soda).
Add wet ingredients for the cake batter (vegan buttermilk and oil).
Put approximately 1/3 of the batter in a separate bowl. Add in chocolate batter ingredients (cocoa powder and soy milk). Set aside.
In the mixing bowl with 2/3 of the batter, add vanilla sugar. Adjust consistency with soy milk if needed. Both batters must have same consistency.
In a parchment-lined round cake pan, add barely enough vanilla batter to cover bottom of the pan. Then, in the center of the vanilla batter, add a few tbsp of chocolate batter, don't go to the edge. Repeat steps until you run out of batter.
Bake at 180°C for 25 min or until you insert a toothpick in the cake and it comes out clean.
For the ganache: melt chocolate combined with milk in microwave at 30 sec increments. Stir in between. Add salt. Pour over your cake. Smooth out quickly with a spoon. Let cool and enjoy :)