Herby Pistachio and Feta Dip

A beautiful, faintly Middle Eastern, pale green dip fit for royalty or, at least, people you really like. Roasting pistachios brings out their slightly sweet flavour, which works so well with salty and tangy feta. This recipe is very adaptable: feel free to use whatever soft herbs you like and add as much garlic and lemon as tastes good.