For preparing Pacha Thakkali Theeyal, first heat up a pan or kadai.
Fry grated coconut, till it turns brown.
Before switching off the flame, add coriander powder and fry for a sec.
Switch off the flame and add the chilly powder and mix well.
Allow it to cool.
Grind it along with enough water to make a smooth paste.
Heat oil in a pan or a kadai.
Splutter mustard seeds and saute red chillies and curry leaves.
Add onions and green chillies and saute well.
When it gets sauteed well, add sliced tomatoes and saute again.
Add turmeric powder, salt, coconut paste and enough water and mix well.
When it reaches the desired consistency (which is neither too thin nor too thick), remove Pacha Thakkali Theeyal from flame.