To prepare the saffron water, crush the saffron and sugar using mortar and pestle till powdery. Add the hot water and mix. Set aside.

Drain the soaked basmati rice and set aside.

Boil around 10 cups of water with some salt. Add the drained rice and cook for around 5-7 minutes. Drain. The rice will only be partly cooked. Wash well in cold water.

Wash the barberries well till it is clean. Remove off stems if any. Allow to drain on a kitchen towel.

Heat the butter in a small pan. Add in the barberries and sprinkle the sugar.

Toss well. You will see the barberries slightly puffing up. Take off the heat. Add 2 tbsp of the saffron water and mix well.

Heat up a saucepan till dry. Take off the heat.

Sprinkle in the olive oil and 2 tbsp of the saffron water.

Line up the sliced potatoes at the bottom. This will make up the crust called "tahdig".

Arrange half the rice on top, spread the barberries, and then spread the remaining rice.

Poke in several holes in between, for steam to escape. Close the lid.

Keep on high flame for five minutes.

Now lower the flame to the lowest possible, take off the lid and sprinkle in the remaining saffron water.

Cover the lid with a kitchen towel and keep it tightly closed.

Cook undisturbed for 30 to 45 minutes.

Just before serving, take off the lid, and give it a good mix. The potato would look crusty.

You can serve the mixed rice with the potatoes, or serve the potato crust separately.