Here is something I baked just before I went away, sadly I forgot to take many pictures as it got eaten very quickly. However I can verify that it is a very nice cake, the natural yoghurt makes it extremely moist and it is very satisfying to have with your afternoon cuppa.
Vanilla and chocolate marble cake
200g caster sugar
tsp vanilla paste
3 large eggs
150g natural yoghurt
170g self raising flour
1/2 tsp bicarbonate of soda
40g cocoa powder
60ml boiling water
40g white chocolate
75g icing sugar
Preheat the oven 180/160 FAN. Grease a bundt tin well, or alternatively grease a 2lb loaf tin and line the base.
Cream the butter, sugar and vanilla paste together until light and fluffy. Lightly beat the eggs, add to the bowl and mix until combined.
Add half the flour and and all the bicarbonate of soda and mix until fully combined. Add half the the yoghurt and mix again. Add the remaining four and mix until combined. Add the remaining yoghurt and give a few more stirs.
Mix the water and cocoa powder to form a paste. Remove ~1/3 of the cake mix into a clean bowl and fold through the cocoa paste until combined.
Put blobs of the two different mixes into the tin, I used an ice cream scoop.
When all the mix is in the tin use a knife to marble the two together, be careful not to marble too much, a few swirls should do it.
Meanwhile make up the white chocolate icing, gently melt the white chocolate and set aside to cool slightly. Mix the milk with the icing sugar and then add the cooled white chocolate and mix until smooth and well combined.
Put the icing into a disposable icing bag and snip off the end. Pipe the icing in a zig zag pattern over the cooled cake.