Heat oil in a pan, add onions and sauté till golden brown. Add ginger and garlic pastes and stir. Add green chilli paste and sauté for five minutes. Add almond paste, khoya and yogurt. Cook on low heat for fifteen to twenty minutes. Add white pepper powder and stir. Add chicken pieces and cook further on low heat for ten minutes, stirring occasionally. Pour in one cup of water and simmer for another five minutes. Once the chicken is cooked, add cream and stir. Add green cardamom powder and rose petal powder, simmer for two minutes and remove from heat. Garnish with silver varq, almond and pistachio slivers. Serve hot.