Trim fat from meat, cut meat into 5cm (2in) squares; flatten well with meat mallet. Put meat in bowl with soy sauce, salt, pepper, curry powder, ginger, bicarbonate of soda, sugar, sherry and oil. Mix well, allow to marinate at least 2 hours or, covered, overnight in refrigerator. Heat extra oil in large pan, add meat slices to pan, spreading slices out; do not allow slices to overlap; brown well on both sides, remove from pan. It may be necessary to do this in small quantities. Rince and wipe pan, add peeled and quartered onions, cubed peppers, cornflour mixed with water, crumbled stock cube, extra soy sauce, sherry and sugar. Bring to boil, stirring. Cook 2 minutes or until vegetables are cooked but still crisp. Return meat slices to pan with meat juices, toss lightly until heated through.