The Pan Bagnat aux Anchois is the reading of the sandwich tuned around the anchovy. Where most pan bagnat treats the anchovy as one salt note among several, this version gives it the lead: salt-cured anchovy fillets laid across the oiled crumb of a split round country loaf in enough quantity to flavour the whole sandwich, with hard-boiled egg, olives, tomato, raw onion, and a lighter hand of tuna built around them. The dressing stays olive oil and a touch of red-wine vinegar, the loaf is weighted and rested, and the anchovy's salt and depth run through the soaked bread rather than appearing only when a bite happens to find a fillet.
The anchovy-forward build is distinct because of what the fish does to the dressing during the soak. Salt-cured anchovy releases into olive oil as it sits, so over the rest the fillets soften and their savour diffuses into the crumb, which means the seasoning is carried by the bread itself and very little added salt is needed anywhere else. That intensity sets the limits. The bread has to be the sturdy, faintly tart Niçois-style round, because the dressing here is doing heavy work and a weak crumb would simply turn to oil-soaked pulp; the tomato and egg have to be generous enough to round the anchovy's edge, or the sandwich reads as one flat salt note. Done in balance it is the most savoury and the most marine of the pan bagnat readings, a sandwich whose character is set before it is ever bitten, eaten by hand at the beach or market rather than at a table.
Variations turn on how far the anchovy is allowed to dominate. Some hands keep a measure of plain tuna alongside for body and to soften the salt; others go nearly all anchovy and lean on extra tomato and egg to carry it. A few crushed olives push it darker still; more raw onion sharpens against the cure. The inherited orthodoxy holds throughout: no mayonnaise, no cooked vegetables, the bread soaked rather than crisp, the sandwich better for its first hours of rest. For the full account of the soak, the bread, and the Niçois rules this version inherits, see Pan Bagnat.