Step 1

Bring a large pot of well-salted water to a boil.

Step 2

Place the rice in a large bowl, rinse with cold water and drain in a colander until the water runs totally clear. Drain well.

Step 3

Add the rice to the pot and boil until the grains are soft on the outside but still hard at the center, about 6 minutes. Drain the rice and rinse under cold water.

Step 4

Measure out 1 1/4 cups of the parcooked rice and transfer to a bowl; stir in the yogurt, the 1 tablespoon melted butter and 1/4 teaspoon salt.

Step 5

Melt the oil and the remaining 1 tablespoon butter together over medium-low heat in a 2- to 3-quart nonstick pot with a tight-fitting lid. Add the yogurt rice and spread it evenly to cover the bottom of the pot. Add the remaining rice, mounding it into a pyramid shape. Insert the handle of a wooden spoon into the mound 3 or 4 times to make vents for steam to escape. Increase the heat to medium-high and cook until the rice starts to steam, about 2 minutes. Reduce the heat to medium-low and cover the pot, first with a clean towel and then with a lid. Steam until the rice is fully cooked and a golden brown crust has formed on the bottom, about 50 minutes.

Step 6

Spoon the loose rice onto a platter, then use a firm spatula to remove the crust from the pan. Top the rice with the crust and sprinkle with the parsley and sumac if using. Serve immediately.