Take the curd and besan in a bowl.
Whisk them to a smooth paste.
Add 2 glasses of water and whisk again to a lump-free mixture.
Use a hand-held blender or a balloon whisk for this purpose.
Mix in the red chilli powder and turmeric powder.
Keep it aside till the tempering is prepared.
Heat the oil in a thick bottom pan on low heat.
Add the mustard seeds and the cumin seeds.
Let them crackle.
Quickly add the grated ginger, curry leaves, hing and the slit green chillies.
Let them cook for a few seconds and then put in the curd mixture.
Add salt and sugar.
Add more water if needed.
Let it simmer for about 10 minutes or till it gets the desired consistency.
The kadhi tends to thicken a little bit on keeping, so adjust the water quantity and cooking time accordingly.
Lastly, garnish with fresh coriander leaves and serve hot with boiled rice