Marinate the beef cubes with all the ingredients listed under 'for marination'. Let it stand for 15 minutes.
Pressure cook the marinated beef till it is done. (No need to add any water as the water content in the beef is enough to get it cooked).
Heat oil in a large pan and splutter the mustard seeds. Add onion, curry leaves and saute till the onion starts to brown. Add the cooked beef, garam masala and pepper powder, stir well until the gravy is completely dry and becomes dark in color.