Two steps down the road
Before reading on, give yourself a few minutes to try and solve this problem :
If you found it, congratulations ! I didn't. 
And I think this kind of position is extremely challenging, because you have to overcome two successive hurdles :
- looking for forcing moves and correctly calculating the sequence up to Bxc7 (this is the relatively easy part)
- down there, spot that there is still something to play for (the white king has no squares), and find or retrieve the mating net pattern
That's what strong tactics boil down to : a good thinking process (forcing moves first !) and a nice pattern bank to know when it's okay to stop calculating, and when there may still be something to find...
As promised, here is another example from one of my training games :
