This is traditional Maharashtrian soup/curry base made from buttermilk.

Ingredients:
1 cup Cooked Kulith (Horse gram) Stock
(Excessive water from Cooked Kulith)
1 cup Sour Butter milk
1 Green Chili
1/2 Tsp Ghee
1/4 Tsp Cumin seeds
Pinch of Asafoetida Powder
Salt to taste
1 tbsp chopped Cilantro

Method:
1) In a saucepan, take Horse gram stock. On low heat, make it lukewarm. Then add Buttermilk to it.
2) Finely chop green chili. Crush green chili coarsely with salt. Put crushed chili into Kulith Stock and add more salt if needed.
3) In small saucepan, heat 1/2 tsp ghee. Add Cumin seeds and asafoetida powder. Put this tadka to Horse gram stock. Do not heat much. Kalan is served at warm temperature and not hot.
4) Sprinkle chopped Cilantro. Serve as soup or with rice.

From My blog : http://chakali.blogspot.com/2008/05/kulathache-kalan_13.html