225g/8oz caster sugar
200g/7oz icing sugar
225g/8oz self-raising flour
75驳/2陆辞锄 walnuts
12 walnut halves, to decorate
225g/8oz unsalted butter, softened, plus extra for greasing
125g/4陆oz unsalted butter
4 free-range eggs
50ml/1戮fl oz strong espresso coffee
50ml/2fl oz strong espresso coffee