These are a kind of sushi-style take on a classic combination of smoked salmon and crème frache inside a pancake. You can make them up the day before, keep them in the fridge wrapped in cling film, then slice them up at the last minute. They look great if you serve them up-ended, like sushi-rolls, on a rectangular or square plate with the dip in a little bowl. You could use mustard mayo or even horseradish sauce instead of the vinaigrette dip if you like.