Cook the meat pieces well in 1 dsp of vinegar, water and salt. Remove from fire with 11/2 oz of gravy. Once it cools, keep the gravy aside and mince the meat pieces well. Cook the potato also, peel and mash it well with out any lumps and keep aside.
Saute the minced onion, ginger, green chillies in oil. Add the meat also, sauteing it well. Put the minced tomato. Stir well till it is dry. Finally, add the gravy and when it dries up, remove from fire and let it cool.
Mix the mashed potato with the cooked minced meat. Make balls the size of a lime each and flatten and shape smoothly, as you like.
Beat the egg with 2 dsp of water. Dip each cutlet in the egg, then coat it with bread crumbs. Deep fry in oil till the outer cover turns golden brown in colour.