Chess960: Opening Puzzle No. 6

I kid you not this puzzle came from a blitz Chess960 game less than ten moves old. The solution is actually quite clever and therefore I missed it! (Note that the chess engines take quite a few seconds to find this idea and if you wind the position back a couple of turns along it's forced line they take a lot longer):

SP244 Black to move: find the only winning move

The answer obviously involves how to catch the white bishop in the most efficient way.
Solution is given somewhere on this page. Enjoy 960!

1.       ... Ba6! and white is lost
2. Nxc6? ... Rc8
3. Ne5   ... Qe7 -/+ (white's bishop will fall)
if
2. c3    ... Rc8
3. f3    ... Qe7
4. fxe4  ... QxB -/+


In other words Ba6! clears the c8 square for Rc8 and preventing blockage of the 7th rank so that white's bishop can be captured by the queen. At the same time Ba6! prevents any quick exit plans for white's queen and is actually a developing move. All other solutions fall back to mediocrity. Note that white's last ditch effort to capture a pawn with Bxb6 does not work because it gives a free developing move to black with ...NxB.