Heat oil in a pan, add the skin, along with tamarind and saute it until the skin turns slight brown, remove from heat. Now add red chillies and saute it. Grind all the ingredients with salt and sufficient water.
In a separate pan, heat oil and add mustard seed. When it stops spluttering, add urad dal. Saute for a min and add it to the thuvaiyal.
Delicious Peerkangai Thol Thuvaiyal is ready to be served.
Serve this thuvaiyal with idli/dosa/chapathi/rice and enjoy.