Firstly, the marinade. And secondly, the Tandoori oven. It's a combination of these two elements that give tandoori dishes their wonderful flavour, moisture and texture.
The tandoori marinade can be applied to anything from chicken to fish to vegetables to paneer but the traditional dish is made with chicken. Usually, it involves removing the skin from a whole bird and slashing the flesh to ensure that the flavours from the spices in the marinade infuse into the meat.
This is a two stage process and varies from one recipe to another but I like to crush fresh ginger, garlic, chilli, salt and lemon juice and smearing this all over the bird. While this is doing it think I make up my flavoured yoghurt. In India they would use hung yoghurt which is yoghurt that has had the water removed from it by hanging in a muslin. This makes the marinade really thick. You can easily replicate this or you can use half cream and half yoghurt too. To the yoghurt I like to add a few choice spices such as cumin, garam masala, Kashmiri chilli powder and fenugreek so it becomes really fragrant.
The iconic thing about this dish is it's colour which is bright red. This colouring comes from either the Kashmiri chillies or beetroot powder. They do use this in India but you can miss it out if you want to.
It's the oven that gives this dish is distinctive smokey flavour and soft texture to the meat. The tandoori oven's unique design means that food cooks very quickly because it can reach up to temperatures of about 450°C. It's designed to be a cylindrical, bell shaped oven made from clay which radiates the heat back into the cooking area. They used to be built into the ground and the wood or charcoal heat source sits in the bottom of the oven itself which exposed the food to live fire. The fat and juices dripping on to the coals produces the lovely smokiness which in turn adds depth to this dish.
At home I usually cook this on the bbq to try and replicate these flavours. If I cook this in the oven I also mustard oil for added pungency and cook on a high heat to get a little bit of charring on the meat.