1 tsp baking powder
225g/8oz light brown muscovado sugar
150g/5½oz icing sugar, sifted
225g/8oz self-raising flour
75g/2½oz walnuts
25g/1oz walnut halves
250g/9oz fudge, roughly chopped
225g/8oz butter, softened, plus extra for greasing
150g/5½oz butter, softened
4 large free-range eggs