Ginger and treacle cake

1 tsp ground ginger

1 tsp ground cinnamon

½ tsp nutmeg

175g plain flour

75g butter, cubed

75g treacle

75g golden syrup

75g dark muscovado sugar

½ tsp bread soda, sieved

2 tbsp milk

2 tsp fresh ginger, finely grated

1 egg, lightly beaten

To decorate:

150g icing sugar

3 tbsp orange juice — a little more if needed

a handful of unsalted pistaccio nuts, deshelled and roughly chopped