Seal the venison loin in a very hot pan for 3 minutes until evenly browned all over.
Coat the meat with the mustard and black pepper, then wrap very tightly in cling film and chill for 1 hour.
For the dressing, combine all the ingredients in a bowl and whisk until emulsified, then season.
To serve, slice the venison very thinly with a sharp knife and place onto your chosen serving dish.
We use a polished shoulder bone for an added bit of theatre, but a nice plate or wooden board will do just as well.
Garnish with a piece of shaved Parmesan, capers, watercress and a sprinkle of sea salt.