This classic Provençal sandwich, which means "soaked bread" in the ancient Nice dialect, is nothing more than a Salade Niçoise served between two pieces of bread. In the old days, it was considered to be a humble food, made with ingredients that every household would have on hand.
But today pan bagnat is fashionable fare. And for good reason: It makes an extraordinarily delicious and satisfying meal.
In my version, the grilled peppers add a bit of depth to this simple sandwich, and the basil vinaigrette soaks the whole thing with its ambrosial fragrance — making it the quintessential summer sandwich!
Preheat the grill on medium-high heat.
Brush the peppers with the olive oil and set aside on a tray. When the grill is ready, place peppers directly on the grill, cut side up, and grill until charred, about 4-5 minutes.
Turn the peppers over and grill until well charred, about 3-4 minutes. Transfer to a tray and set aside. (Alternatively, you can roast the peppers under the broiler, following the same directions as for grilling them.)
Place all of the ingredients in the bowl of a food processor and process until the basil is very finely chopped and the vinaigrette is smooth. Transfer to a bowl and set aside.
In a small bowl, mix the olives and capers. Set aside.
Lightly toast the cut side of the rolls on the grill or under a broiler. Drizzle both sides of the rolls with two-thirds of the vinaigrette to soak the bread. Top the bottom half of each roll with the grilled peppers, olive-caper mixture, scallions, and the egg slices.
Drizzle with the remaining vinaigrette. Top with the tomatoes and cucumber slices. Season with salt and pepper, to taste. Finish with the top side of the rolls, press slightly with your hand, and cut the sandwiches in half. Serve with a leafy green salad with mustard vinaigrette.