For the chicken, spatchcock the chicken and peel off the skin as best you can. With a sharp knife cut incisions into the chicken so the marinade can really absorb. Season chicken with salt.
In a bowl, mix all the tandoori mix together and then massage into the chicken. Leave for at least 24 hours.
Heat the grill to its highest setting. Preheat a griddled tray lined with foil and place the chicken under the grill or barbeque and cook for 45-50 minutes until cooked through. If flesh begins to burn turn heat down a little.
Leave to rest for 30 minutes.
For the onion bhaji, heat the fryer to 165°C.
Slice onions, then salt lightly and leave for 5 minutes until the onions begin to bleed. In a pestle and mortar place the cardamom pods and grind, then add the remaining spices. Add the spices, gram flour and chopped coriander to the onions, mix well until you have a dropping consistency. Shape into handful size flat discs or to whatever size you prefer then deep fry for around 7-8 minutes (shorter time if smaller) until golden crispy brown. Repeat until mix is used up.
For the raita, mix together all the ingredients and serve chilled.
On a large serving dish lay the iceberg to create a bed. Place the chicken on top then arrange bhajis around chicken. Garnish lemon wedges and coriander. Serve raita in bowl and naan if required.