Wash the rice in cold water in a large bowl, then rinse and drain it. Repeat the process with more cold water until the water runs clear. Cover the rice with cold water, add a generous fistful of sea salt to the water and allow the rice to soak for 2-3 hours. (Soaking isn’t essential, but even 30 minutes soaking time will help elongate the grains, making for a more elegant rice dish.)
Finely chop the herbs and spring onions, or alternatively pulse them in a food processor in two batches until finely chopped. Set aside the herbs then add the spring onions to the food processor and chop as before. Add to the herbs and set aside.
Place a large saucepan or stockpot over a medium heat. Fill the pan with boiling water, drain the rice and add to the pan along with another generous fistful of sea salt, the chopped herbs and spring onions. Stir well and allow to boil for 6-8 minutes, or until the rice is parboiled (when the grains turn from the normal whitish opaque to a more brilliant white, although they will not have become fluffy yet). Drain the rice and herbs in a colander and set aside (do not rinse).
Return your pan to the heat and add the oil, a few generous knobs of butter and a tablespoon of sea salt. Scatter the rice into the pan. Ensure you scatter it – don’t pack it - because you want the lightness of the falling rice to allow for steam to rise up. Add the remaining butter. Wrap the pan lid in a tea towel (to lock in the steam and make a secure, tight seal), cover the pan and cook for 8 minutes on a medium-high heat. Then reduce the heat to low-medium and cook for a further 25-30 minutes.
Once the rice is cooked, remove it from the pan (I like to place a large serving dish over the pan and flip the rice on to the dish), then scrape out the tasty tahdig (meaning ‘bottom of the pan’ – this is the crust bit every Persian fights over) and serve this on top of the rice.