Pre-heat your oven to 177 Celsius (350 Fahrenheit). Grease two 20cm x 10cm cake loaf tins with vegan butter then set aside. 

Make your vegan buttermilk. Measure out the soy milk then add the apple cider vinegar to it. Give it a mix then set aside for 7-8 minutes until it curdles. Measure out the other ingredients while you wait.

To a large mixing bowl, add the flour, sugar, baking powder, baking soda & salt. Mix well. 

Next, pour in the curdled soy milk, oil and vanilla. Don't mix at all. Using a wooden spoon, fold the ingredients together by slowly scooping the mixture over itself. Keep folding the dry into the wet until there are no more pockets of flour. This takes a little longer than mixing but it results in a much better cake. Patience is key! 

Equally divide the cake batter between the two greased loaf tins and bake in the centre of the preheated oven for 20 minutes. A skewer should come out clean at this point. 

 Remove your cakes from the oven and let them cool in the tins for 15 minutes. Then remove the cakes from the tins and transfer them to a cooling rack to cool fully. Don't apply anything to the cakes until they have completely cooled down.

Add the vegan butter block to a stand mixer or a large bowl and cream for 2 minutes.

Next add half of the powdered sugar. Beat the buttercream mixture until it is fully combined and has began to thicken. Then add the rest of the powdered sugar. Beat again until your buttercream is nice and thick. 

Now add the cocoa powder. Mix until it is fully combined within the buttercream.

Spread half of your chocolate buttercream in between the cake halves and spread the other half on top. Enjoy!