Steam the liver until cooked (cook for only 10 mins, otherwise, the liver will harden).
Slice liver into thin, 1 inch, long pieces.
Grind coriander powder, chilli powder, turmeric powder, cinnamon, cloves and cardamom into a fine paste.
Heat oil in a pan.
Add mustard seeds and when they splutter, saute onion.
Add ginger and garlic and stir for a while.
Add the ground paste and saute.
When the oil starts to separate, stir in the liver.
Add vinegar and salt to taste.
Sprinkle crushed pepper and saute.
When the gravy thickens, remove from fire.
:- Serve hot.