Put onion,
garlic, ginger, fresh coriander into the container of electric blender.
Blend to a
smooth puree.
Heat oil in a
heavy saucepan and fry the blended mixture, stirring for about 5
minutes.
Add turmeric,
garam masala, salt and chili powder and fry for a further minute.
Stir in
yoghurt and tomatoes, and fry until liquid dries up and the mixture is
the consistency of thick puree.
Add chicken
pieces, turning them in the spice mixture so they are coated on both
sides, then turn heat low, cover tightly and cook until chicken is
tender.
If liquid
from chicken has not evaporated by the time the flesh is cooked, uncover
and raise heat to dry off excess liquid, stirring gently at the base of
pan to prevent burning.
Garnish with
chopped herbs and serve with rice or chapatis.