A speciality of the city of Shiraz. This soup is given texture with chopped walnuts, and an unusual flavour from the herb fenugreek, called shanbalileh in Iran.
Melt the butter in a large pan. Fry the onions in it until they are a pale golden colour. Add the flour and stir over very low heat for a few minutes until well blended. Add the walnuts and fenugreek. Pour in a ladleful of the hot water and beat vigorously, then add the rest of the water gradually, stirring constantly. Season to taste with salt and pepper, bring to the boil slowly and simmer, c