1. Put yogurt in a medium bowl. Heat 1/4 cup oil in a small skillet over medium-high heat until hot. Add 1/2 teaspoon mustard seed. Cook, shaking, until seeds pop, about 45 seconds. Add curry leaves; cook until starting to wilt, about 1 minute. Add ginger and chopped chiles. Cook, stirring, 30 seconds. Stir in turmeric. Pour mixture over yogurt. Stir in salt and sugar. Transfer to a serving dish.

2. Heat 2 tablespoons oil in a small skillet over medium-high heat until hot. Add 1/2 teaspoon mustard seed and the whole chiles. Cook, shaking, until seeds pop, about 45 seconds. Garnish dip with chile mixture and curry leaves. Serve with papads and persimmons, if desired.