Just wanted to add a little note to say that I threw one of these together earlier and it turned out very well. Thanks very much for posting a fantastic recipe.
Some specifics for anyone else planning to make one: I used ChewyTikka's mix powder and base gravy and found that they worked perfectly well. For the quantities of onion and pepper, I used a quarter of a medium onion, in long, thin slices, and about a quarter of a green pepper, similarly chopped. My chutney was Patak's brand. Served with plain boiled rice.
A beautiful savoury dish that was really easy to put together.