A traditional korma will have a long slow cooking. In fact, korma is not one particular dish but rather a method of cooking similar to braising. Because korma is a cooking method there are a wide variety of dishes that could be described as "korma". Many kormas call for the meat to be marinated in yoghurt and then the meat plus marinade are braised on a very low heat until all the juices condense down into a thick sauce. The restaurant chef has to cook to order so doesn't have time for long, slow cooking. The korma you find in Indian restaurants usually contains ground almonds, coconut and thick cream. It is often described on restaurant menus as being "very mild" but a good korma should not be bland.
Chicken Korma is a dish originating in the Indian subcontinent, consisting of succulent pieces of chicken braised with yogurt, stock, and spices to produce a thick sauce. A mild curry for those with a delicate palate but a thirst for adventure.