Jerry,
As with all recipes, each component must play it's part as a whole. If the balance is wrong it affects the others and has a dramatic effect on the results. I learnt this with Methi leaves which I love, but add too much and it can kill a dish.
Your mention of the White Pepper and Fennel in the Lasan recipe stands out to me. White pepper is not something I generally like and I tend to notice it in recipes where it is used. It's certainly noticeable in several of our local BIR/TA's.
Have you tried replacing the Fennel with Aniseed? I know how much a difference this can make, from my visits to the IG Kitchen.
The other thing that I feel is quite important is making sure the marinade not to thick that it clings to the meat like a paste. I get much better results this way as a pasty marinade tends to burn before the meat is cooked and makes the finished dish bitter.