Heat oil in a pan and add in the fennel seeds. Let it splutter. Then add in the finely chopped onions, curry leaves and fry well till its brown.
Crush the green chillies, garlic and ginger in a mortar and pestle. Add it to the onion mixture and saute for a minute. Run two tomatoes in a mixie / blender to form puree. Add in the tomato puree.
Add half a cup of water (I use water left over from boiling vegetables), salt, turmeric powder, chilli powder and coriander powder. fry till all the mixture is dry and streaks of oil starts to appear on top.
Then add in the boiled potatoes and peas. Add in the pepper powder. Mix well to combine. Saute for a couple of minutes. Add in the chopped coriander leaves and remove from heat.