Chocolate marble cake  with mocha glaze

INGREDIENTS

butter 100g, softened, plus a little for the tin

self-raising flour 150g, plus a little for the tin

% dark chocolate 75g, chopped

milk 150ml

250 g

light muscovado sugar

eggs

25 g

good-quality cocoa

 butter 125g, softened

180 g

 golden caster sugar

eggs

180 g

self-raising flour

150 g

soured cream

vanilla essence a few drops

6 tbsp

icing sugar 

3 tbsp

good-quality cocoa

very strong coffee 1 tbsp, freshly made