Add all dressing ingredients to a blander and blend for about one minute, or until smooth. Taste and add a bit more lemon juice or seasoning if needed. Keep the dressing in the refrigerator until needed or up to a week.
Cook the couscous according to instructions on the package. Clean all the vegetables and fruits under cold running water. Chop the celery stalks. Halve, destone and scoop the avocado flesh onto the board, chop it on small cubes, drizzle with a bit of lemon juice, to prevent oxidation. Peel and grate the carrots. Peel the orange and mango, cut both into small chunks. Roughly chop large salad leaves.
Drain the couscous and tip on to a salad bowl. Add all the vegetables and fruits to the salad bowl. Toss with the salad dressing. Sprinkle with half of the chopped fresh herbs. Mix well and season to taste. Serve with a dollop of greek yogurt and a bit of tabasco. You can also serve with flat bread or tortilla.