For what it's worth, when I did my 737 TR in July, we practiced both "AF447" and "Turkish at Amsterdam" stall scenarios. In the case of the high-altitude stall, the recovery method we were taught, and that worked very well, was to get the nose well down, apply full thrust, and let the speed build to VREF40+100. We were also taught to use 230KIAS as a ballpark figure. Do NOT start pulling up until the tip of the speed vector touches 230, at which time you gently recover back to level flight. This method worked really well. We tried pulling up earlier, and most of the times this resulted in a series of secondary stalls and a massive altitude loss until you got down to thicker air. Nevertheless, we lost 7-10 000ft from FL400 before recovering, even with the correct procedure.