Do the eggs:
I put them in a pot with water, bring that to a boil and let it boil for 3 minutes. Then turn off the heat and let the eggs sit there for another 5.
Peel the eggs (helps to cool them down in ice water first)
Do the salad:
Chop the eggs, parsley, celery and mix with a spoonful of mustard, one of mayo, and cornichons or capers.
Season with salt and pepper and lemon juice (and cumin, delicately).
Do the sandwiches:
This makes two big sandwiches. Heap on the salad and add arugula. Cut them in half (if you're feeling classy). Put some extra salt on there for good measure.