You will need –
2 cups sour curds or 4 cups butter milk, 1 inch ginger, 3 green chillies, 2 tblsp. besan (gram flour), salt and jaggery to taste (or sugar), a few curry leaves, 2 tblsp. ghee, 1/2 tsp. mustard seeds, 1/2 tsp. methi seeds, 1/2 tsp cumin seeds, 1/8 tsp. asafoetida, 1/3 tsp. turmeric (optional).
Churn the curds or butter milk together with the gram flour, Add water to give a thin consistency. Grind ginger and chillies and add to the mixture. Add salt and jaggery (or sugar). Bring to a boil, stirring frequently. Reduce the heat to very low and keep boiling for ten to fifteen minutes. Heat the ghee, add mustard seeds, methi and cumin seeds and asafoetida. Add the curry leaves and turmeric (optional) and pour the boiling ghee on the kadhi. Cover immediately; and take off the heat. After a few seconds, remove cover and mix well. Serve hot.