Grind the mango marination mixture and add it to curd and mix it well.
Now ,wash nicely the chicken pieces and dry them with the help of a tissue paper. Add the chicken pieces to mango curd mixture and keep them aside for about 30 mins.
Take half chopped onions and tomatoes and grind them together to a fine paste.
In a heavy-bottomed pan heat oil and add half the chopped onions and fry them well until they turn light brown.
Add coriander powder,chicken masala,pepper and salt and mix them well.
Now add the remaining kept chopped tomatoes and cook them covered for about 2-3 mins.
Add the tomato-onion paste and bring it to boil.
Add the marinated chicken and mix well. Allow them to cook with closed lid and occasionally keep stirring in between.
After 15 to 20 minutes adjust the salt and add more chillies,Chicken masala to taste and check if the meat is knife-tender but not breaking up.
Remove from heat and garnish with chopped coriander leaves and serve hot with nan or rice.