Whisk the Buttermilk and keep aside
In a kadai, add oil, to it add mustard seeds, black gram, after the spluttering of mustardseeds add curry leaves.
Now add buttermilk, turmeric powder, Chilli powder, Cumin powder, Black pepper powder, Fenugreek powder and required salt to your taste.
Mix well anf bring to boil. Now reduce the flame to low and allow to cook
Now simmer the mixture, till the buttermilk reduces to a thick gravy consistency. This procedure takes around 20 mins for the above quantity.
Remove from heat and serve hot.