To prepare mixture to marinade, take a bowl and mix ginger and garlic paste along with, vinegar, red chilli powder, mustard paste, black pepper powder, all spice powder, salt, chopped capsicums, chopped sweet onions and tomatoes. Mix them well to prepare a fine marinating paste.
Marinate the boneless chicken using mixture prepared in step 1. Leave it for some time to rest.
Take the shashlik sticks and sew the marinated boneless chicken into the sticks.
Now take sizzling platter and heat it well, place the shashlik sticks on it and start cooking them till they get brownish texture.
Take a separate bowl to prepare sauce. Add tomato ketchup in it along with tamarind juice, garlic powder, green chillies, half teaspoon of salt and water. Mix them well to prepare fine sauce.
Pour the sauce created in step 4 on shashlik sticks and serve hot.