Boil the kettle and grind the saffron to a powder using a pestle and mortar. Pour 4 tbsp boiling water over the powder, stir and leave to infuse for 5 mins.

Heat the oil in a large saucepan over a medium-high heat and cook the onions for 12-15 mins, until soft and lightly golden at the edges. Add the chicken and garlic, and season well. Stir, keeping an eye on the heat to make sure it doesn’t brown, for about 5 mins. This is to maintain the golden yellow colour of the saffron, which is important in Persian food.

Pour in just over half the saffron mixture into the chicken, then top up with just enough water from the kettle to cover all the chicken pieces, about 500ml. Simmer gently, uncovered, for 35-40 mins until the chicken is tender.

Meanwhile, cook the rice in a large pan of boiling salted water for about 6 mins, or until the grains are elongated and white, but not fully cooked through. Immediately drain in a fine sieve and rinse well under cold running water to remove the starch, using your hands to sift through and make sure every grain is rinsed. Drain well and leave to rest for 10 mins, shaking off any excess water.

Remove the chicken and onions to a plate using a slotted spoon, reserving the cooking liquid. Set aside.

Pour enough water into a non-stick pan (with a lid) to cover the base by about 1/2cm (do not use a cast-iron pan, as it will conduct too much heat and scorch the rice too quickly). Mix the yogurt with the remaining saffron, the oil and some salt, then pour this into the pan and stir into an even mixture.

Halve the rice mixture and scatter (but do not compress) into the pan, ensuring it goes to the edge. Carefully lay the chicken and onions into the pan, then season with a little salt. Add the remaining rice on top. Wrap a cloth around the lid, then use it to tightly cover the pan. If using a gas hob, cook over the lowest heat for about 1 hr. If using induction, cook over a medium-high heat for 45 mins.

Meanwhile, melt the butter in a pan, turn off the heat and fold in the barberries, pistachios, almonds and sugar, and set aside.

To serve, remove the lid from the pan and gently fold the nut and berry mixture into the rice. Serve most of the rice on a platter, then remove the tahdig (crispy crust), cut into triangles and put on top of the rice. Reheat the chicken broth and serve on the side, if you like.