Melba toast may seem a bit dated, but there’s no better accompaniment for a salmon mousse. To make it, all you need to do is toast the bread on both sides, cut the crusts off and slice in two horizontally, turn the untoasted side up and rub off the excess bread with your fingers, toast it again, and that’s it. Don’t leave the blender on for too long when you make the mousse, or the mixture may split.