Soak tamarind in 1 cup water for 15 minutes.
Heat 1 tablespoon oil to a medium sized pan heated on medium to high flame.
Add shallots and sauté until golden brown.
Extract tamarind concentrate and add to the shallots.
Add asafetida and sambar powder along with rest of the water and allow the mixture to come to a boil.
Lower the flame to low to medium and let the mixture simmer while boiling for 10 to 12 minutes or until shallots turn soft and sambar powder loses its raw flavor.
Mix in mashed dal and adjust the salt.
Cook for 2 to 3 minutes more.
Remove from fire and keep aside.
In a small pan, heat rest of the oil.
Add mustard seeds and allow to splutter.
Add curry leaves and green chilies and sauté for 30 seconds.
Pour this mixture over sambar and mix in coriander leaves.
Hot, yummy sambar is ready to be served.