Stuck it in problemiste, you'll be happy to know that the solution is unique. Here is the complete solution. (please bear in mind Problemiste is German, S = N!)
Solution: 1. Qf6! [2. Sh6, Rxg7#]
1. ... Qb8/a8/e8/d7/e6, Rb6, Ra6, Rc7, Rd6, Re6, Rc5, Rc4, Rc3, Rc2, Rc1, Bd4, Bc3, Bb2, Ba1 2. Sh6, Rxg7#
1. ... Qd8 2. exd8=Q/R, Sh6, Rxg7#
1. ... Qf8, g6, Bxf6 2. Sh6#
1. ... Qc7/b7/a6 2. e8=Q/R, Sh6, Rxg7#
1. ... Qxf5 2. e8=Q/R, Rxg7#
1. ... g5 2. Sh6, Rxg5#
1. ... h6/h5, Rxf6 2. Rxg7#
1. ... Bf4 2. Qxg7, Rxg7#
1. ... Bxg3 2. Qxg7#
1. ... Bd6/c7/b8 2. Qxg7, Sh6, Rxg7#
A while ago, I posted a topic looking for a certain mate-in-two puzzle I'd seen before; but at the time I was unable to find anyone else who'd seen it and my attempt to reconstruct the puzzle was rather crude. So now, I decided to take a crack at it again and I think I managed to create a better version than before; getting rid of the large material disparity in my first attempt and removing a couple of weirdly-situated minor pieces and a pawn. Still, I'm not entirely sure whether the new version is cooked or unsound, so I figured I'd post it up here and see if anyone spots any loopholes in it. Feedback would be much appreciated.
(Variations are given in the movelist. However, thanks to the inherent nature of the puzzle, there are multiple solutions to some Black responses...I'm just interested in making sure there is only one key first move, and that all Black responses to that move allow a mate in one.)