Rinse rice in 2 changes of cold water; drain. Bring rice and 4 cups water to a boil in a large saucepan. Add oil and salt. Cover, reduce heat, and simmer 15 minutes or until liquid is absorbed. Fluff with a fork. Spoon rice into a large bowl; let cool to room temperature. Add yogurt, mango, buttermilk, and cilantro; stir gently.
Heat ghee in a small skillet over medium heat. Add mustard seeds; cook 3 minutes or until seeds begin to pop. Add remaining ingredients; cook 2 minutes or until fragrant. Pour over rice mixture. Discard chiles, if desired. Serve immediately.