Fry the onions in the butter until golden.
Add the rice and dill stalks; stir round the pan.
Pour in the saffron stock, bring to the boil,
then cover and simmer for 5 mins. Add the
beans and half the dill. Cook 5 mins more
until the liquid has been absorbed into the
rice. Meanwhile, stir the yogurt, milk and garlic
together with seasoning. Spoon yogurt on top
of the rice, then sprinkle with remaining dill.