Crush sundakkai, wash it well and keep it aside.
In a pan, add chana dal, sundakkai, chilly powder, turmeric powder, salt and water and mix well.
Cover and cook for a few minutes on medium flame until sundakkai and chana dal are cooked well.
Once cooked well, drain out the water completely and keep it aside.
Heat oil in a pan.
Add mustard seeds, urad dhal, curry leaves and crushed garlic and saute well.
Add chopped onion and green chili and saute on low flame until it turns golden brown.
Add asafoetida and mix well.
Add cooked sundakkai and stir well.
Finally, add coconut and mix well.
Sundakkai poriyal is ready to serve.