For the vinaigrette:
Cut the prunes in half and put in a small pan with the water. Bring to a boil and simmer, uncovered, for around 10 minutes until the water has almost all gone. Turn the prunes once or twice as they are cooking so both sides soften.
Remove from heat and transfer to a small food processor. Add the oil, balsamic vinegar and Dijon mustard and blend until fairly smooth. Add 1 tbsp. water, or a little more/less as needed to get a gently pourable thickness.
For the salad:
While the prunes are simmering, put the couscous in a heatproof bowl (e.g. glass). Boil water and pour over the couscous so it is covered and the water is around ¼ in. (2/3cm) over the top.
Cover and leave to expand.
Meanwhile, thinly slice the radishes and cut the pepper into small chunks. Finely chop the parsley and cut the prunes in quarters. Remove the fleshy part from the preserved lemons and finely chop.
Once couscous is ready, fluff it up with a spoon/fork and mix through the prune vinaigrette. It will become a bit sticky but don’t worry. Add the radishes, pepper, prunes, preserved lemon and almonds and mix well. Serve or pack to take with you.