Ive just made this Rogan Josh with chicken, I really like the idea of the 2 stage approach.
I didnt use this base (used the 600ml oil one with chick stock, by the way this base sauce with chicken stock cold has the smell of that taste in it). I didnt use curry powder either, I used pataks kashmiri paste instead, my initial tasting says ive overdone it on the spices (I cooked this for 2 so doubled up on the spices which was about 3 desert spoons of the paste).
I have cooked it in advance so havent eaten it yet (of course! ;D), Ill eat it in a few hours and report back