How about mate in 3...bh6#
Mate in 7
Yeah Why is Nf4 forced if he takes the bishop it leaves a way out... I dont think its truly mate in seven.
1)...ng4+ kf4 2) nf3e5 nd6+ 3) ke7 nxb7 4) d5 kg5 5) bf6+ kf4 6)g5#
as far as the game being played as was:
1)...ng4+ kf4 2) nf3e5 nd6+ 3) ke7 ne4 4)bh6#
This position came up in a game I played recently in the live chess area. I didn't see it of course! I did end up mating in a really asthetically pleasing way, but I could have done it much earlier. Which is for you to figure out. Good Luck!
Some might find other mates as I have, but no less than 7 moves.