Tahdig

Rinse the rice in several changes of cold water until the water runs clear, then leave it to soak in fresh cold water for 1 hour.

Meanwhile, grind the saffron threads to a powder with a pinch of the salt, then stir in the water, freshly boiled, and leave to steep for 15 minutes. This is the saffron water.

Bring a large pot of water to the boil with the rest of the salt. Drain the rice, add it and boil for 5 to 7 minutes, until the grains are soft outside but still firm in the centre. Drain and rinse briefly.

Separate the egg. Mix 2 large spoonfuls of the par-boiled rice with the yoghurt, the egg yolk and half the saffron water.

Heat the oil in a heavy non-stick pot and spread the saffron yoghurt rice over the base, pressing it flat. This layer becomes the crust.

Pile the rest of the rice on top in a loose mound, poke 5 or 6 holes down to the base with a spoon handle, and dot with butter.

Wrap the lid in a clean tea towel, tie the corners up over the handle so they stay well clear of the flame, cover tightly and cook on medium heat for 10 minutes, until you hear it sizzle, then on the lowest heat for 45 to 50 minutes.

Uncover, lift 3 or 4 spoonfuls of rice from the top into a bowl and stir in the remaining saffron water. This is the saffron rice.

Take it off the heat, run a knife round the edge, put a plate over the pot and invert it in one confident movement. Scatter the saffron rice around the crust.