Dissolve ground saffron in 1/2 cup of boiling water and set aside (click for How to Use Saffron).
Pick over the dried barberries (zereshk) and remove any stones. Then wash and drain. In a small pot, melt the butter over medium-low heat. Add the barberries and saute for 1 minute. Add the sugar, cinnamon, and salt, and saute for 1 minute. Add the dissolved saffron and cook for 3-5 minutes. Set the barberry mixture aside.
Meanwhile, prepare the plain rice (click for Persian Rice recipe). When rice is ready, in a large bowl mix 1 1/2 cups of cooked rice with the barberry mixture. Add the slivered pistachios and stir.
To serve, place a layer of plain rice on a serving dish then a layer of barberry-rice mixture. Repeat the layers and serve with Cooked Chicken.