The secret to achieving the smoky flavor in this raita lies in allowing the dried chiles to roast in the oil until they are blackened. The smoky heat leaves a lasting impression even when masked by the heat-lowering, creamy-tart yogurt.
Whisk the yogurt and salt together in a medium-size bowl.
Heat the oil in a medium-size skillet over medium-high heat. Add the mustard seeds, cover the skillet, and cook until the seeds have stopped popping (not unlike popcorn), about 30 seconds. Stir in the chiles and cook until they blacken, 15 to 20 seconds.