The Hardest Checkmate in 1 move Puzzle

It is White to Play and checkmate the black king in only 1 move. Calculate deeply how white can checkmate the  king in one move. White has 9 checks in this position. 1. If either rook captures the pawn on f7 then the king can go to h8. 2. The queen has 3 checks.  If Qxg6+ the hxg6. If Qf6+ then the king can capture the knight on h6. If Qxe5+ then it will be captured by dxe5. 3. The knight on g3 can give check on h5 then the king can still go to h8. If either knight goes to f5 then the king can again go to h8. 4. The light squared bishop cannot give any immediate check. The dark squared bishop can play Bxe5 but then it will be captured with dxe5. None of the standard checks work to deliver checkmate. It has to be a special rule like castling, promotion but that is not the case. Another special rule is called en passant when a pawn moves two squares from its original square beside a pawn on the 4th/5th rank and the pawn can be captured as if it had only moved one square forward. It has to be done immediately and cannot be made in the subsequent moves. We need to figure out what was black's last move. 

White pawn D5 wins the game, Black moved the pawn, En Passant wins by revealing check from the black square bishop.

The pawn on f7 cannot block the check by moving to f6 because of the rook pin on the 7th rank. Thanks for giving the answer.