I do a cold infusion for 24 hours to reduce the amount of tannins I'm getting in the infusion. Mjx, with the way you do your infusions - boiling twice - do you find that you get a lot of tannins? I warm my cream at the beginning and end (and boil it once it's strained for shelf life purposes) to help coax the oils out but I'll bet you'll get more of the oils with boiling. Perhaps I'll try that next time.
I haven't had noticeably tannic results with this method. I've also steeped more leaves as briefly as 3 minutes, and the flavour has been intense and complex.
I never boil the cream with the leaves in it: I boil the cream, remove it form the heat, add the leaves, steep, remove the leave, and bring it just to a boil once again, before combining it with the chocolate.
I've made several tea ganaches, and have had excellent results from steeping a pinch the leaves (in a tea bal) directly in warm cream for about a quarter of an hour.
I forget which chocolatier recommends boiling the cream twice, but essentially, that's what I do: boil the cream, steep the tea in it, bring it once again to a boil, remove the tea ball, and carry on.
This is exactly how I do it as well! Except I just dump the tea in and strain it out :D
I've done that too, but putting the tea in a tea ball (or my tea shark) does makes for slightly quicker leaf removal :)