How to Make It
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.
Urad dal may be purchased online.