Step 1Cook the rice as you would pasta: Bring a large pot of lightly salted water to a boil. Add the rice and cook until it is tender, 10 to 15 minutes. Do not overcook or undercook it; the rice should be soft all the way through but should not be beginning to "explode" at the ends.
Step 2Line a jellyroll pan with a kitchen towel. Drain the rice and rinse it quickly under cool water, then spread it over the kitchen towel. Cover with another kitchen towel and gently pat dry.
Step 3Meanwhile, put the cucumbers in a large bowl with the parsley, dill and mint. In a small bowl, combine the green onion, vinegar, oil and one-fourth teaspoon salt.
Step 4While the rice is still warm, transfer it to a bowl and add the cucumber mixture, dressing and yogurt, and toss gently with a wide rubber spatula. Taste for salt and tartness.
Step 5Serve tepid or chilled, mounded on plates and garnished with light green lettuce leaves.