Chop potatoes into big pieces (8 or 10, each potato).
Heat oil, add cumin and mustard seeds, allow to splutter.
Add ginger, garlic, stir, add onion, saute for a minute.
Add tomato, stir and cook till oil separates.
Add all masalas, salt, curds and stirfry till boil resumes.
Add potatoes and peas, 1/2 cup water and bring back to boil.
Allow to simmer, covered, till gravy is thick, stirring occasionally.
Serving :
Garnish with Chopped green coriander leaves.
Goes well with Chapathi,Naan or Rice.