Preheat your oven to 160C fan. Line a 2lb loaf tin (standard size) with greaseproof/parchment paper. With a loaf tin always make sure the parchment paper goes over the edges to help you lift the finished loaf out.
Cream the dairy free spread and caster sugar together until pale, light and fluffy. I use my electric hand mixer.
Add your eggs gradually. Mixing thoroughly in between each, also add your vanilla.
Fold in your flour, xanthan gum and baking powder. Make sure everything is thoroughly mixed in.
Split the cake mixture into two separate bowls.
In a small bowl, mix your sieved cocoa powder and milk (or hot water) together until perfectly smooth (if hot water allow this to cool).
Once cooled add to one of your bowls of cake mix, mix it in thoroughly.
At random spoon in your cake mixture into the tin. I tend to spoon one chocolate, followed by one vanilla etc this will ensure you get a marbled effect. Continue till the mixture is used up.
I like to then use a skewer to gently swirl my cake mixture a little more before placing in the oven.
Bake in the oven for 55-60 minutes, until cooked completely through.
Leave to cool in the tin for a while before placing on a cooling rack to completely cool.
Once cool make the icing. Melt your dairy free spread in a pan and add sieved cocoa powder. Mix it in and heat gently for around a minute.
Stir in your dairy free milk and icing sugar. Then remove from the heat and mix thoroughly. Keep stirring for a minute or so and the icing should thicken up nicely.
Spread the icing evenly oven the cake.
For a final (optional) touch melt a little dairy free white chocolate and using a piping bag drizzle it over the top. Allow all the icing to completely set.
* For the cake mixture, if you prefer you can use the all-in-one method. I've tried both ways and I just prefer the fluffiness that the creaming in method seems to provide. Both methods make a great cake though!