This endgame composition, by Kubbel in 1922, is one of my favorites. First, it looks impossible because that black pawn seems destined for greatness. Secondly, you learn that every piece and pawn on the board has a purpose. That knight way over on b8 helps in the win. The bishop has an obvious role. And what about those two pawns for White? Work this one before you escape to the answer. It will be very satisfying as you eliminate what doesn’t work and find out the one line that does!
1.Nc6 Kxc6 [1...a2 2.Nb4+] 2.Bf6 Kd5 3.d3 [3.c4+ Kxc4]3...a2 4.c4+ Kc5 [4...dxc3 5.Bxc3]5.Kb7 Kd6 [5...a1=Q 6.Be7#]6.Bxd4 and wins.