Pan bagnat (Provencal tuna sandwich)

Vinaigrette: combine the salt, Dijon and freshly ground pepper, add the vinegar, then whisk in the olive oil.

If the emulsified dressing is too thick, thin it with a drop of cold water.

Cut the bun in half and pull out some of the inside crumb to make room for the filling, without making a hole in the bread.

On the bottom half layer julienned green and red bell pepper, thin-sliced red onion, cored tomato slices and torn basil; drizzle with a few drops of dressing.

Add flaked tuna, a few drops more dressing, then pitted black olives (cut and pit them if not pitted).

Optionally add a couple of anchovy fillets, more basil, then thin-sliced hard-boiled egg.

Spread a little dressing on the top half and drizzle everything with a little olive oil.

Close and press the top onto the filling so the flavours soak into the bread. Make ahead wrapped in aluminum foil and refrigerated, or let stand 20 minutes to half an hour before serving.