Methods

1. Fill a large stock pot with 4 quarts of water and bring it to a boil over high heat.
2. In the meantime, place the rice in a bowl and rinse with cold water, swirling vigorously with your fingers and changing the water at least five times, until the starch has run off and the water runs clear. Drain the rice.
3. Once the water comes to a boil, salt it heavily. The precise amount will vary depending on what salt you’re using, but it’s about 6 tablespoons fine sea salt or a generous half cup kosher salt. The water should taste like the saltiest seawater you’ve tasted. This is your big chance to get the rice seasoned from within, and it’s only going to spend a few minutes in the salted water, so don’t panic about oversalting your food. Add the rice, and stir.
4. Set a fine mesh sieve or colander in the sink. Cook rice, stirring from time to time, until it’s al dente, about 6 to 8 minutes. Drain into the sieve and immediately begin rinsing with cold water to stop the rice from cooking further. Drain.
5. Remove 1 cup of rice and combine it with the yogurt.
6. In a mortar and pestle, grind the saffron into a coarse powder. Mix with the boiling water and set aside.
7. Set a large, very well seasoned 10-inch cast iron skillet or non-stick frying pan over medium heat, then add the oil and butter. When the butter melts, add the yogurt-rice mixture into the pan and level it out. Pile the remaining rice into the pan, mounding it gently toward the center. Sprinkle the reserved saffron water over the top of the rice. Using the handle of a wooden spoon, gently dig five or six holes into the rice down to the bottom of the pot, which will be gently sizzling. The holes allow steam to escape from the bottommost layer of rice so that a crisp crust can form. There should be enough oil in the bottom of the pan so you can see it bubbling up the sides. Add a little more oil if needed to see these bubbles.
8. Continue cooking the rice over medium heat, turning the pan a quarter turn every 3 to 4 minutes for even browning, until you start to see a golden crust begin to form at the sides of the pan, about 15 to 20 minutes. Once you see the crust turn from pale amber to golden, reduce the heat to low and continue cooking for another 15 to 20 minutes. The edges of the crust should be golden, and the rice should be cooked completely through. There isn’t a way to tell what tahdig will look like until you flip it, so I prefer to err on the side of overbrowning, but if that makes you uncomfortable, pull the rice after about 35 minutes in the pan.