Dissolve the saffron in a few tbsp of freshly boiled water. Keep it in a warm place until you use it later.
Heat 2 tbsp of vegetable oil in a pan and fry the chicken leg from each side, until golden brown. Remove it from the pan.
Place the chicken leg in a small pan, that has a lid, and add 250 ml (1 cup) of freshly boiled water to it. Peel the onion and make two cross shaped cuts into it from the top, half way down. Add it to the pan, together with the black pepper, half of the saffron water and salt to your liking. Put on the lid and let it simmer over low heat for about 1 hour.
Once the chicken leg is cooked, remove it from the pan and let it cool. Don’t throw away the chicken broth. Remove the onion and serve it later as a sauce for the Tahchin.
Wash the rice in a bowl with water by just moving it around with your hand. Then drain the water and repeat these steps a few times.
Bring lots of water to boil in a pan. Dissolve 2 tbsp of salt in it (no worries, any excess salt will be washed off later, but trust me without this amount of salt your rice will taste bland). Add the rice, stir it well and allow the water to boil again.
Let the rice pre-cook for a few minutes. The cooking time depends on the rice you are using. Remove a rice corn from the pan after about 3 minutes and split it with your fingernail. If the outside is cooked but the centre of the rice corn is still firm, it is ready and can be drained and rinsed now. Think of it as half cooked pasta for a pasta bake. It might take anything between 3 to 7 minutes for your rice to get to that point. I used Tilda basmati rice and 3 minutes were enough.
Drain the rice in a strainer and rinse it with cold water. Stir it with a spoon while you rinse it to make sure that the excess salt washes off and that it cools down to interrupt the cooking process.
In a bowl combine the egg with the yoghurt, rest of the dissolved saffron, and a little salt. Add the rice to it and stir it well until it turned evenly yellow.
To be on the save side, select a coated pan. I used a 16cm (6.3″) diameter pan for a small, high Tahchin but you can also use a larger pan for a shallower Tahchin. Melt the ghee in the pan. Make sure not only the bottom but also the sides of the pan are lined with ghee or butter.
Pull the chicken leg from the bone and tear it into pieces, like in the picture below.
Add half of the rice to the pan, then spread the chicken out evenly on top of it, leaving a bit of space between the sides of the pan and the chicken to make sure it remains hidden inside the rice cake.
If you are preparing a small Tahchin for 4 people like I did, you will probably only have two layers of rice with one layer of chicken in between. If you are doubling the ingredients to make a larger Tahchin though, you can make more layers to make sure the chicken is evenly distributed throughout the Tahchin.
Sprinkle 1 tbsp of freshly boiled water on top and poke a few holes into it (all the way to the bottom of the pan) with a bamboo skewer or a long toothpick. Place the pan over medium to high heat. Once you see steam rising from the rice, put on the lid and reduce the temperature to low. You can cover the lid with a clean kitchen towel. Let the Tahchin cook for 1h.
Wash the barberries and briefly fry them in 1 tbsp butter or ghee with 2 tsp sugar. This shouldn’t take longer than 10 seconds, otherwise the barberries will burn. Combine the barberries, sugar and ghee with 1 tbsp freshly boiled water and the slivered almonds and pistachios. Set it aside for later.
Put on some oven gloves, remove the lid from the pan and put a serving plate upside down in its place. Carefully flip the pan over and remove it.
Decorate your Tahchin with the barberry pistachio mixture. Serve it with the chicken broth and yoghurt. Enjoy!