What an interesting little puzzle.
White to move and moves his bishop (lower right) up and to the right for checkmate. But, black has a response of double pushing his pawn still in its starting position up two to interpose, allowing a discovered checkmate by his bishop. At which point white takes blacks double pushed pawn "en passant" or 'in passing'. Now, interestingly enough, that would mean that black never actually got out of checkmate. The reason why you can double push your pawns is to speed up the game. The en passant move is so that people cannot abuse it to avoid being attacked by the other players pawns. So really the double pressed move is suppose to be two moves with only the opportunity by the other player to capture on the very next move or rather in the middle of the move that was just made. But, it's treated like a single move. So who really wins? Can black interpose if black can't reach the needed square? Because the whites response sets back the clock so to speak? Or does black win because the interposing allows for a discovered mate? Should you be allowed to capture the king in passing?