Nicoise Salad is sort of flexible. Everyone has their own version and even the lettuce is optional!
The only really non-optional ingredient is good tuna.
Either fresh lightly seared tuna steak or a good quality canned tuna. High end Spanish or Italian canned (or jarred) tuna, is increasingly available at gourmet food stores and worth a few extra dollars. You can even make your own canned tuna. I’ve never tried it but I hear it’s awesome.
I suppose you’d have to say that nicoise olives are non-optional as well, but don’t let that stop you if you have the other ingredients around.
I like to use a classic Dijon Vinaigrette with this.
Ingredients – in order of likelihood to show up in a Nicoise Salad recipe:
Nicoise olives (or other small ripe olives)
sliced hard-boiled egg
Boston or bibb lettuce, or the salad greens of your choice
anchovy filets, de-salted (soaked)
boiled small red potatoes
lightly cooked green beans
sliced green and/or red pepper
marinated artichoke hearts
blanched fava beans