Heat the oil in a pan; add the onion and garlic and sauté for a while. Add the gram flour and sauté lightly making sure that the colour of the gram flour does not change. Set aside to cool.
For the first marinade, mix together the ginger-garlic paste, salt, white pepper powder and vinegar. Rub the mixture into the chicken and set aside for one hour in a refrigerator.
For the second marinade, put the cashew nut paste into a bowl. Add the roasted gram flour mixture, cream, ginger-garlic paste, salt and white pepper powder and mix well. Put the marinated chicken in this mixture and rub well. Set aside to marinate for three hours in a refrigerator. Preheat the oven to 200°C/ 400?F/Gas Mark 6. Thread the marinated chicken pieces onto skewers and cook in the preheated oven for ten minutes basting with melted butter. Turn over, baste with melted butter again and cook the other side for ten minutes.
Alternatively cook the chicken in a tandoor or over a charcoal grill for six minutes, or until partially cooked. Baste with melted butter and cook for another three to four minutes.
Serve hot with a salad and chutney of your choice.