That's an interesting appraisal of the Kushi method MM. It's a looong time since I made Kushi style but I do remember not being overwhelmed with the results...nor underwhelmed for that matter. It just struck me as a nice curry but nothing special and not the BIR taste I was after...but then it is a Balti book!
So your amendments, at least I assume they are amendments, where you say "key" do look like the sort of things that would get it more Baltified, especially the extra boiling and base for a thicker, more scoopable, end product. Oh yes and why in particular do you feel the Dutch onions are important?
I might revisit this now.