Preheat the oven to 180C. Grease two, 4 inch bake tins, line them with parchment paper. I have used 2 pans, you can also combine and bake in one single pan.
In a large bowl, sift together whole wheat flour,cocoa, baking soda, baking powder and all the spice powders along with salt. To this add sugar and whisk well to combine.
In a small bowl, combine egg replacer powder and water, mix well and let it sit for a minute or two to thicken.
In a measuring jug, take buttermilk/laban, add oil to it, whisk well to combine. (See notes)
Now to the flour mix first add the buttermilk-oil and using a electric beater/whisk combine, as you combine add the egg replacer mixture and sweet potato puree to this and whisk well to combine.
The batter might be too thick, if thick, the add another 1/4 cup of water to it and combine
Divide the batter into two prepared cake tins. Bake the cake for 45-50 minutes or until a skewer inserted in the middle comes out clean.
Once done, remove the cake from the oven, let it sit for 5 minutes, then un-mould the cake onto a wire rack and let it cool completely.
Allowing the cake to rest is very important before removing the cake from the tin. Been there and done that, be patient or you will end up with half the cake in the pan and half in your hand.