Peel out the potatoes and make it into pieces.
Soak the pieces in water.
Cut the tomatoes into pieces.
Always wash the tomatoes before cutting.
Heat oil in kadai.
Add 1 tsp kala jeera.
Let it splutter, then fry the potatoes in it.
Add 1 tsp salt and turmeric powder in it.
After the potatoes get fried put the tomatoes. (But Fry the potatoes in slow flame.)
Don't add water as tomatoes leaves water.
Add the mustard paste.
Let it simmer on slow flame covered with lid.
After the potatoes get boiled, add coriander leaves into it. (Always remember the coriander leaves should be washed properly in the running water so that mud should not be there.)
Serve it with Rice or Roti.