Whisk together besan and yogurt till smooth. Add ginger-green chilli paste and 2 cups water and mix well. Add salt and mix.
Heat ghee in a deep non stick pan. Cut potato and radish into thin strips. Add mustard seeds, asafoetida, cinnamon, cloves, cumin seeds, red chillies, curry leaves, potato and radish to the ghee and mix well. Cook for 2-3 minutes.
Add ½ cup water and cook till potato and radish get cooked.
Add yogurt mixture and mix and cook till the mixture thickens slightly. Add sugar and mix well.If using banana, peel and slice it and add it to the kadhi. Serve hot with steamed rice.