Arguably, there are 3 types of Indian cuisine, apart from the many regional variations.
Originally what is now India and Pakistan were unified and it is only in relatively recent years that India was partitioned into India, East & West Pakistan (1947). Later East Pakistan split and became Bangladesh (1971). When, due to the desire to dominate the spice trade, Britain became involved in the affairs of India the East India Company was created (circa 1620) and eventually became the dominant force in the region. The British employees of the East India Company were happy to integrate into Indian society and embraced many features of the local culture. The cuisine however was not always compatible with the European taste and a hybrid cuisine that might be called Anglo Indian developed to suit the British palate. When these employees returned to their home country the desire for curry returned with them. At that time it was difficult, if not impossible, to obtain the necessary ingredients so adaptions were again made to the recipes. In addition native Indians from the Syhlet area came to Britain on the trading ships and eating places for these native Indians began to emerge. It was from these origins that the Indian restaurants developed. As the desire for fast food, often as an accompaniment for chips, developed, another new style of Indian cuisine emerged that has come to be called, restaurant, take away or BIR (British Indian Restaurant) style. This latter style owes very little to traditional Indian cuisine but it is what most of us in Britain think of when we think of curry. Traditional cooking techniques had to be abandoned in order to provide a fast and economical service.

The High-Street Flavour

Traditionally, many curries were cooked 'long and slow', and, as previously mentioned, when Indian food became popular in the West, some way had to be found to speed this process up so that restaurants and 'take-a-ways' could produce a meal in an acceptable time. Additionally many of the recipes were adjusted to accommodate the 'less sophisticated' Western palate. For this reason a style of cooking was adopted for the high street restaurant that has produced a characteristic flavour that has been difficult to re-create at home. Most recipe books for Indian food are written in the traditional home-style and can therefore be disappointing to those making these recipes, as the result is not quite what was anticipated. So is it possible to recreate the restaurant flavour? Certainly it is; you just need to know the process restaurants have adopted to provide a fast food service. It must be said that some restaurants still adopt a more 'à la carte' approach which may mean a longer wait but a more traditional style and taste. It's all a matter of which you prefer.

The method

The first requirement for a quick curry is to produce a basic cooking sauce and to pre-cook the meat. The content of this sauce is a closely guarded secret with each restaurant having its own special recipe causing each restaurant to have a characteristic background flavour. The meat is precooked and used in the majority of curries on the menu. That's not quite true with Tikka and Tandoori as these are quite distinct usually being marinated and cooked at high heat on skewers. The pre-cooked meat may well be refrigerated in bulk and used and replenished as needed with the cooking sauce (base sauce) being made daily.
Restaurants will make many litres of base sauce at a time - very impractical for the home kitchen - but the base sauce recipes in the BIR section of this site produce reduced quantities much more suitable for the home cook/chef.