Ingredients:

2 tablespoons gram flour/besan
3 cups water
2 teaspoons oil
½ teaspoon cumin seeds/jeera
2 green chillies
2 inch piece ginger, ground to a paste
2 sprigs curry leaves/patta
Salt
1 pinch turmeric/haldi powder (optional)
2/3 cup thick, creamy coconut milk (use more than ½ cup if not very creamy)
1 lime

Preparation:

See how to make coconut milk.
Prepare slurry of besan in 3 cups of water.
Fry the jeera in 2 teaspoons oil. Upon spluttering, add slit green chillies, 
ginger paste, and curry patta.
To this seasoning, add the besan slurry and salt to taste. If yellow kudhi is desired, add a little haldi as well.
Bring the liquid to a boil.
Reduce heat, add coconut milk and simmer for a minute. (It is extremely important for the flame to be low and to heat the coconut milk for a short while or else it will split.)
Remove from fire, add lime juice.

Serve hot with rice.