Gently wash the rice in cold water until the water runs clear. Place in a bowl and fill with cold water to 2 inches above the rice. Let the rice soak for a minimum of 30 mins (preferably overnight).
Take a saucepan and add 2 tbsp of vegetable oil and place on a medium / high heat,
Add the diced potatoes and fry until they turn golden and a little crispy. Then add the onions and fry until they soften and turn translucent.
Then add the garlic, turmeric and tomato purée and stir until evenly distributed in the mixture.
Add the chopped fresh tomatoes, the bloomed saffron, fresh herbs and seasoning. Stir and cook for a few minutes. Turn the heat off and leave the mixture until you are ready to add to the rice.
Drain and put the rice in a saucepan and add the vegetable stock and 1 tsp of salt (I use a standard UK 20 cm saucepan with a glass lid, 2.5 litre capacity).
Put the saucepan on a high heat until the water starts to boil. Once the water comes up to the boil, turn the heat to medium and add the butter /ghee / oil and stir gently to mix.
Once you start to see holes forming in the rice (as the water is evaporating), take the temperature down to the lowest setting. Take the potato and tomato mixture and pour into the rice. Gently stir into the rice mix whilst trying to avoid breaking the rice grains.
Then take a clean tea towel and wrap the lid of the saucepan, making sure it is not a fire hazard. Place the lid on the saucepan. The tea towel will help the steaming process and soak up the water, preventing it from falling back into the rice and making it mushy. Leave the rice cooking for 45 mins or more. The longer you leave it, the better the crispy layer that forms at the bottom of the pot (tahdig).
Once you have come to the end of the cooking time (45 mins or more with the lid on), turn off the heat and dish up the rice on to your plates or serving dish. Plate up your tahdig as well.
Serve with salad or yoghurt, and / or eggs.