Preheat your oven to 180°C (350°F). We will start by creating a vegan buttermilk. In a bowl, mix the soy milk with apple vinegar and let it sit for 5 minutes to curdle.
Now mix the dry ingredients. In a separate bowl, whisk together the flour, sugar, ground hazelnuts, cocoa powder, salt, vanilla sugar and baking powder.
The next step is combining the wet ingredients. Add the oil to the vegan buttermilk and stir until well combined.
Gradually pour the wet mixture into the dry ingredients, stirring until the batter is smooth and lump-free.
It's baking time! Pour half of the batter into a greased cake pan and bake for 30-35 minutes, or until a toothpick comes out clean. Repeat this process with the other half of the batter, so you get two layers of cakes.
Let the cakes cool in the pan for 10 minutes, then transfer to a wire rack to cool completely before decorating them with speculoos cream and garnishing it to serve it.