In a small bowl, stir the crushed saffron threads into the warm milk.
Set aside for at least 10 minutes to allow the saffron to bloom and infuse the liquid with its color and aroma.
In a medium saucepan with a tight-fitting lid, melt the butter over medium-low heat.
Add the currants, chopped pistachios, and rice.
Stir continuously for 2-3 minutes to toast the grains until they become fragrant.
Pour in the water, salt, sugar, ground cinnamon, and the saffron-infused milk. Give everything one final, gentle stir to combine.
Increase the heat to high and bring the mixture to a full boil. Immediately reduce the heat to the lowest possible setting, cover the saucepan with the lid, and let it simmer undisturbed for 25 minutes.
Remove the pot from the heat and let it stand, still covered, for an additional 5-10 minutes to allow the steam to settle. Fluff the rice gently with a fork before serving immediately.