Whisk together yoghurt, besan, turmeric, salt and water until the mixture is smooth and no lumps remain. Using a large strainer, strain the liquid for good measure and, add grated ginger and chilli and set aside.
Heat ghee in a large pan. Add cumin seeds and mustard seeds and sauté until the seeds sizzle and pop.
Quickly add the asafoetida and curry leaves and sauté for 15 seconds or until fragrant.
Slowly pour the liquid to the spices and bring the mixture to a boil, stirring constantly.
Reduce the heat and simmer for 10 minutes, stirring occasionally.
Turn off heat, add chopped coriander and serve with rice or kichdi.