Grease a 15-inch oval glass baking dish or a 9x13-inch rectangular glass baking dish with ½ cup of the oil.

Rinse the rice in a fine-mesh sieve until the water runs clear. Transfer to a large bowl and cover with room temperature water. Soak for 30 minutes to 1 hour, then drain.

Using a mortar and pestle, grind the saffron threads and a pinch of salt into a fine powder. Add the ice cubes and let them melt to create the saffron water — this will take about 20 minutes.

Meanwhile, preheat your oven to the broil setting and position a rack in the upper third of the oven. Arrange the eggplant slices in a single layer on two parchment-lined baking sheets. Using the remaining oil (but saving the last teaspoon), brush the eggplant with  oil. Broil one sheet at a time until the eggplants are deeply golden and slightly charred, about 5 minutes. Flip, brush with oil again, and broil for another 3 minutes. Sprinkle with a pinch salt immediately after removing from the oven. Repeat with the second tray.

Lower the oven temperature to 350F.

Place 1 teaspoon of oil into a small skillet over medium low heat. Add the barberries and stir. Cook for about 5 minutes or until the barberries are fragrant and slightly plump. Set aside.

Bring a large pot of water to a boil. Add 7 tablespoons of salt. Add the drained rice and cook for 6 to 8 minutes, until par-cooked (al dente) with a slight bite. Drain well.

In a large mixing bowl, whisk together the eggs, saffron water, lemon juice, and 1 teaspoon of salt. Gently fold in the parboiled rice until evenly coated.

Spread half of the rice mixture evenly in the prepared baking dish. Sprinkle with ½ cup of the barberries. Arrange the eggplant slices on top in a single layer. Cover with the remaining rice, smoothing the top. Tightly cover the baking dish with aluminum foil.

Bake the tachin for 2 hours, until the bottom is golden brown. (You can peek through the glass bottom pan to check). Remove from the oven and let rest for 5 minutes.

To unmold, place a serving platter (larger than the baking dish) over the top. Carefully flip the dish onto the platter and lift the baking dish away. (Wear oven mitts or use kitchen towels as the dish will be hot).

Garnish with the remaining barberries and serve.

Tachin can be stored in an airtight container in the refrigerator for 4-5 days.