Preheat the oven to 180C / Fan 160C / Gas Mark 4. Line a 2lb loaf tin with a loaf tin liner and set to one side.
Blitz the pistachio kernels in a food processor to a fine crumb. A few lumpier bits is ok as it adds texture to the cake!
Add the sugar and butter to a large mixing bowl and beat with an electric mixer until creamed together.
Add the eggs and briefly mix again.
Add the flour, pistachio nuts and milk and mix together until everything is combined, then pour into the lined loaf tin.
Bake for 50-60 minutes until the cake is risen nicely and a skewer inserted in the middle comes out clean. Remove from the oven and cool in the tin.
Once cooled, remove from the tin and place on a board. Melt the white chocolate in 10-second intervals in the microwave (or over a pan of hot water) and then drizzle over the top of the cake. Scatter with extra crushed pistachios and leave to set before slicing and serving.
Notes
Using Plain Gluten Free Flour? If you don't have any gluten free self-raising flour, make your own by using 125g (1 cup) plain gluten free flour + 1.5 tsp baking powder + 0.25 tsp xanthan gum. Mix well before adding to your cake mixture.