Has anyone got the book Rasoi by Vineet Bhatia. It's the poshest curry book I have.He has a restaurant just off the Kings road in London. The page on spices is in tersesting its separates the spices into sweet and savory. It also goes through the sequence of spicing and says spices generally used in three stages.
1. To temper
2. To create the foundation of the dish.
3. To add aroma.
Tempering:
Oil is heated in a pan over a heat, then whole or lightly crush spices are added. Heating the oil to nthe right temperature is crucial in this process. Too cool the flavours will not be released to hot you will burn the spices.
After brief cooking, a moist ingredient is added, such as onions, Ginger or garlic paste, tomatoes or yogurt, to reduce the temperature of the oil.
creating a foundation :
Spice powders are generally added half way through the cooking a stew, masala or sauce. As they are in power form they blend in easily that acts like a binding agent bring all the ingredients together.
Adding aroma:
This is the final stage of a dish, the equivalent of the french monter au beurre. It is here that the garam masala powders, which give the Indian cuisine its wonderful aromas, are added whetting the appetite in anticipation. The same spices that were used for tempering the dish are lightly roasted and ground before stirring in. The final spice blend should always be used in moderation- generally not more than a pinch.
tadka:
this process in generally used when a dish is made without the intital tempering or when a very intense flavour is needed a lentail stew or raita, for example . The oil is heated to a high temperature (but not smoking) then whole spices are added and instantly to prevent them from burning, poured into the finished dish