Grind the raw mango, coconut, mustard seeds, green chillies, turmeric, and some salt to a smooth paste with some water.
Beat the yogurt till smooth.
Mix the yogurt and mango-coconut paste.
Add some water, if the consistency is too thick, and mix well.
If needed, add some salt, and mix well.
In a ladle, heat the oil.
Add mustard seeds and wait till they crackle.
Add the split red chillies, curry leaves, and asafoetida; and stir-fry for a few seconds.
Add the tempering to the Mavinakayi Tambuli and mix well.
Serve Mavinakayi Tambli with some rice and papad.