1. Roughly chop 250g of the smoked salmon, put into a food processor and pulse to a coarse paste. Add the cream cheese, cream, lemon zest, half the juice and a good grind of black pepper and pulse to a fine paste.
2. When you’re ready to serve, fill the croustades with the mousse and top each with a small piece of the remaining smoked salmon. Squeeze over the remaining lemon juice, scatter over the chives and serve.
Tips: Make sure the ingredients are really cold so that the mousse doesn’t split. You could use smoked salmon trimmings for the mousse. To make this really posh, top each with a little caviar.