Get as much weight forward as you can pronto - slide seats forward and move any items with much weight foward if you can - and hope that this is enough to nudge the nose down towards a conventional spin in time for you to recover normally when (and if!) the flight controls regain their effectiveness.
Could also try applying power with control column fully forward to induce a pitch down I suppose.
That's all I can really think of ... although I suspect that I might also suddenly find religion and pray furiously as a back up plan in such circumstances!
... but only after completing the above actions as best I could.