Persian Tahdig Rice - cooking recipe

Ingredients

1 teaspoon saffron threads
1/2 teaspoon white sugar (optional)
4 tablespoons boiling water
2 cups basmati rice
1 tablespoon olive oil
1 teaspoon salt
2 tablespoons butter, or more to taste

Preparation

Grind saffron threads with sugar in a mortar and pestle. Transfer to a bowl and dissolve in boiling water. Set aside to soak.
Wash starch from the rice by rinsing it in a nonstick 4-quart pot. Rinse 3 or 4 times in lukewarm water until water runs clear. Fill the pot 3/4 full with cold water, covering the rice. Bring to a boil. Add olive oil and cook until rice is soft on the outside and still crunchy in the middle, 10 to 15 minutes.
Drain rice and rinse with cool water. Set aside. Rinse any excess rice starch out of the pot.
Melt butter in the clean, dry pot. Mound rice over the butter; add enough water to reach 1/3 of the height of the rice. Sprinkle salt over the rice. Wrap the lid with a kitchen towel and cover the pot to seal tightly. Simmer over medium heat until all water is absorbed and a crispy crust starts to form on the bottom, about 10 minutes.
Fluff the rice with a fork while turning it out on a plate. Measure 1 cup rice and mix with the saffron water. Scatter saffron rice over plain rice. Detach the layer of crust, or 'tahdig', from the bottom of the pot and serve in a separate dish as a special treat.