How can I imitate the flavor of lamb?
Imitating the flavor of the lamb itself will probably be much more difficult (if not impossible) than manipulating the other ingredients in the dish. That way, the brain is tricked into thinking it is eating lamb, when it is not.  For example, let's say you want to make a meatless lamb biryani.  If you can get the texture of a meatless lamb substitute close enough (for example, by using seitan or some other substitute), then use the proper technique, and ingredients for making a biryani, it will &quot;feel like&quot; you are eating a lamb biryani.
I realize this doesn't directly answer your question, but I think that creating imitation lamb (or any meat) flavor is a difficult problem that challenges food scientists and companies trying to create meatless &quot;meat.&quot;  It would be pretty impressive (and possibly lucrative) if you could easily do that at home, but it would surprise me if it is easy or straight-forward. Brached chain fatty acids could be important, but my hunch is there is a lot more going into how we experience those (or any) flavors.