Just a thought but in the BE post part shown below, he refers to reducing the spicing if using pre cooked ingredients. As most of us presumably use pre-cooked chicken does this mean the base spice quantity needs to be reduced.
Matt
This sauce replaces the one described in the second series of Curry House Cookery. As it is quite well flavoured, it works well with plain cooked meat or chicken. It will produce a perfectly acceptable curry with supermarket bought cooked chicken. If, however, you want to seriously reduce the spicing, then consider pre-cooking the main ingredient with some whole spices.