Grind together coconut, garlic, cumin seeds, turmeric powder, 2 to 3 slit green chillies and a pearl onion into a fine paste.
Mix the paste with the buttermilk and add curry leaves and salt to taste.
Keep on low fire.
Keep stirring till buttermilk is fairly warm. Do not let it boil.
Heat oil in a pan.
Splutter mustard seeds.
Add two finely chopped pearl onions, ginger and remaining green chillies.
When they turn brown, add fenugreek powder and pinch of chilly powder.
Pour the above seasoning into the buttermilk mixture and mix well.