For an exceptionally smooth sauce, you may blitz all Marinade ingredients—excluding the chicken—until silky, though this is optional. In a bowl, combine the chicken pieces with all Marinade ingredients. Cover the bowl and refrigerate for at least 3 hours, preferably overnight or up to a full day. Warm ghee, butter, or oil over high heat in a spacious frying pan. Remove chicken from the marinade but refrain from shaking off excess coating; discard leftover marinade in the bowl for now. Sauté the chicken in the pan for approximately 3 minutes, until all pieces appear white throughout; browning will be minimal due to the marinade. Pour in the tomato passata, cream, sugar, and salt, then add any leftover marinade from the bowl. Reduce the heat to low and gently simmer for about 20 minutes, tasting and adjusting salt if needed. Garnish with fresh coriander leaves if desired, and accompany with fluffy basmati rice.