Step 1

Toast cumin seeds in a dry small saucepan over medium heat, shaking pan often, until fragrant, about 45 seconds. Transfer to a plate and let cool. Coarsely grind in a spice mill or coarsely chop with a chef’s knife; set aside for serving.

Step 2

Heat oil and mustard seeds in a small skillet over medium until seeds begin to pop, about 1 minute. Let cool.

Step 3

Grate cucumbers on the medium holes of a box grater; squeeze out excess liquid with your hands and transfer to a medium bowl. Mix in yogurt, lemon juice, garlic, and ⅓ cup cilantro; season with salt.

Step 4

To serve, drizzle raita with mustard oil, sprinkle with chili powder and reserved cumin, and top with cilantro sprigs.