Wash the rice and soak for 2 hours.
Cooking chelo and polo (traditional method)
Drain the soaked rice. Fill a saucepan three-quarters full with cold water. Add 1 tablespoon of salt per 300 g/11 oz of rice. Bring to the boil on a high heat. Add the rice to the boiling water. To begin with, you will see individual grains of rice rising to the surface as the water boils.
Gradually, more grains come up to the surface with each bubble. After about 10 minutes, you will see the pattern of bubbles change to waves of rice rising to the top. Count approximately five waves and then remove from the heat. Drain in a fine-meshed colander or a large sieve. Taste a couple of grains. If the rice is too salty, rinse once with cold water.
The rice is now ready for steaming. At this stage you can add other ingredients if you are making a polo. Return the empty saucepan to the heat and add vegetable oil (or oil and butter; follow the recipe).
Add your chosen tahdig ingredient . Reduce the heat and gently pile the rice on the tahdig, using a slotted spoon and starting from the middle of the pan. Ideally, you will end up with a pyramid of rice that comes short of touching the lid. This will allow the steam to escape from the sides as well as the top, leaving your rice grains separate and fluffy. Drizzle vegetable oil – or oil and butter cut into small pieces – over the top.
Wrap the lid in a clean tea towel and put it firmly on the pan to prevent steam from escaping as much as possible. The cloth also absorbs the condensed steam on the lid, preventing it from dropping back into the pan and making the rice soggy.
Reduce the heat to low, but make sure that steam rises all the way to the top of the pan. If you have a gas hob, reduce the heat to minimum and use a heat diffuser. Leave to steam for 45 minutes to 1 hour (follow the recipe). It is advisable not to remove the lid during steaming; the crust will form nicely and the rice will not burn. The lid should be hot to the touch and the tea towel should be moist with the steam.