1... Nb5 2. h4 Nc3 3. Ke5 Na4 4. h5 Nc5 5. Kf6 Ne4+ 6. Kg6 Nc5 7. Kf7 Ne4 8. Kg6 Nc5 9. Kf6 Ne4+ 10. Kf5 Ng3+ 11. Kf4 Nxh5+ is your answer. Got any harder ones?
Well it's not a very hard endgame, so you're not going to get anything much harder I'm afraid.
Solved. Took me about 35 seconds
Well done. Quite impressive if you haven't studied the endgame before.