If using cooked rice, skip step 1, and proceed to step 2.) Place uncooked rice in a small colander. Rinse under cold water, using your fingers to move rice around in colander, until water runs clear, about 1 minute. Drain well. Transfer rice to a small saucepan, and add 1 1/2 cups water; bring to a boil over high. Stir once; cover and reduce heat to low. Gently simmer until water is absorbed, about 15 minutes. Remove from heat; let stand, covered, 10 minutes. Spread rice evenly on a rimmed baking sheet; let cool to just slightly warmer than room temperature, about 20 minutes. Divide rice evenly between 2 shallow bowls. Add 1/4 cup yogurt and 2 tablespoons milk to each bowl; gently stir until combined. Stir in salt to taste, and set aside. Heat oil in small saucepan over medium until shimmering, about 3 minutes. Add urad dal and mustard seeds; cook, stirring constantly, 15 seconds (mixture will sizzle). Add chiles and, if using, curry leaves; cook, stirring constantly, until dal turns light brown and curry leaves become almost translucent, about 45 seconds. Immediately pour hot mixture (tadka) evenly over prepared yogurt rice.