I have tried thin pieces, thick pieces, oven light and dark char, chared with a propane torch, long infusion, short infusion, but I still do not get the success you report.
I keep the alcohol at 65ABV, but I find the finished taste still tastes like an old stick, without the vanilla background reported.
I usually tint my alcohol with distillers caramel, as if I leave the oak to achieve the right colour, it seems to produce off tastes.
Whatthe hell am I doing wrong
