Find the winning move!

With my visits to the club heavily curtailed, I have been playing in a 4NCL online tournament, 7 rounds played fortnightly with a time control of 45+15.

This position arose in my latest game as white after my opponent played Bd6-Bb8. I replied Nc2 and ultimately lost a long game. Subsequent computer analysis showed both moves to be blunders, his turning a modest plus for him into +4.6 for me and my reply then returning the favour. I confess my immediate reaction to the computer's suggested move was that it was malfunctioning! Needless to say it wasn't but even once you know there is indeed a winning move, it's not that easy to find and it never even crossed my radar over the board.