Defrost the frozen peas, rinse and set aside
Defrost the chicken legs and remove the skin
Grind the saffron threads with a bit of sugar into a fine powder. Add a some boiling water and set aside to steep.
Ina wide medium pot, place the chicken in and top off with just enough water. Boil for a few minutes, skimming off the top. Then add the onions, cardamom, bay leaf, and season with salt & pepper. Cover and cook for 20-30 minutes until the chicken is tender.
Ina medium bowl, place the rice in and rinse it several times under cold water until it runs clear. Then top off with more water and leave it to soak for 15 minutes. Drain and set aside.
Bring a large pot of water with salt to a boil. Then add the rice and boil for about 10 minutes. Strain the rice and rinse it with cold water to stop the cooking process
Remove the chicken into a bowl and shred with two forks, discarding the bones. Remove the cardamom and bay leaves from the stock, and reduce it further until you have about 1/2 cup of broth with the onions.
Mix the now softened onions with the shredded chicken, and set aside to cool. Preheat the oven to 2000.
In a large bowl, whisk the yogurt, egg yolks, liquid saffron, salt and pepper. Fold the rice in and mix well until it's evenly coated.
Spread butter all over a medium, 2.2 Liter round ovenproof glass dish.
Place half of the rice mixture into the glass dish, pressing down firmly and evenly. Add the layers of the shredded chicken and green peas, and finish off with the remaining rice, pressing down.
Cover the dish tightly with foil and bake for 1-1.5 hours until the base of the dish is crisp and golden brown. Remove from the oven and let it cool slightly.
Once the rice has slightly cooled, run a knife around the edges and place a larger plate over the pot. Hold onto the plate and quickly invert the dish so the crispy rice crust is on the top.
Garnish with barberries and pistachios, and serve alongside a tomato and cucumber salad.