1 litre/1¾ pints whole milk yoghurt OR 500ml/17½fl oz Greek-style yoghurt (It is necessary to have a larger quantity of whole milk yoghurt than of Greek-style yoghurt because whole milk yoghurt will lose more water when drained.)
Line a large sieve with a double layer of paper kitchen roll. Place a bowl under the sieve and pour in the yoghurt. Refrigerate for as long as possible to allow the liquid to drain off the yoghurt. This will take a minimum of 5-6 hours.
Heat a little milk in a small pan. Place two teaspoons of the milk into a small bowl and crumble the saffron strands into it (the rest of the milk can be used in another dish). Allow the saffron to infuse the milk for about ten minutes using the back of a spoon to crush the saffron further into the milk.
Remove the yoghurt from the fridge (the liquid in the bowl below can be discarded). Sift the sugar into the thickened yoghurt, then add the saffron milk and ground cardamom. Cover and chill in the fridge.
To serve, divide the yoghurt among four bowls and garnish with the nuts, silver leaf (if using) and pomegranate seeds.