Yield: 6 - 8 servings
In a large bowl, cover the rice with cold water and 1 tablespoons of the salt. Let soak for 1 hour.
Meanwhile, in a large glass, combine the saffron and boiling water and let bloom until vibrant red, 10 minutes, stir in 1 tablespoon of the salt, 1/2 cup of the oil and 1 teaspoon of the advieh polo spice.
Once the rice has soaked, bring a large pot of water to a boil with the remaining 1 tablespoon of salt. Drain the rice and add to the pot to cook for 5 minutes, then strain.
In a large bowl, stir the yogurt with ⅓ of the saffron mixture. Add 3 cups of the cooked rice and toss to coat.
Great a 4-quart non-stick pot with 2 tablespoons of the butter. Lay the yogurt coated rice along the bottom of the pot and up 1-inch around the edges. Add ½ of the remaining par cooked rice to the pot and drizzle with another ⅓ of the saffron mixture. Dot with ½ of the remaining butter. Layer the remaining par cooked rice on top, then drizzle with the remaining saffron mixture and dot with the remaining butter. Tie a kitchen towel around the lid of the pot and cover (this is to capture excess steam).
Place the pot over medium-high and cook, turning often until you can hear a constant sizzle, 5 minutes. Reduce the heat to medium-low and cook, turning occasionally until the rice is fully cooked and the bottom is golden, 25 to 30 minutes more.**
Meanwhile, in a small saucepan, heat the remaining ¼ cup oil over medium heat with the remaining 1 teaspoon advieh polo, currant and pine nuts. Cook, stirring constantly until fragrant and the pine nuts are toasted, 3 to 4 minutes.
Once the rice is ready, place a platter over the pot and invert to reveal the crispy tahdig. Spoon the currants and pine nuts over top, then serve.
*While yogurt is common for the classic casserole tahchin, Robina uses it for her regular rices or polo to form a richer and thicker crust.
**You can alternatively bake, covered, in a 375 oven (as long as the pot is oven safe) for about 2 hours, which is how you would make tahchin.
