The World’s Greatest Tuna Sandwich

Great tuna and great bread are the core components of pan bagnat. I began by draining a couple of jars of our favorite oil‑packed tuna. As for the bread, the most traditional versions feature a single-serving round roll, but a baguette, ciabatta, or bâtard that French bakers slice and sell by the portion is also common. I settled on a baguette because fewer slices would be necessary to portion the long loaf, which would hopefully allow more of the filling to stay intact. I hollowed out the bottom half—a typical step that makes space for the abundant filling and increases the ratio of filling to bread—and nestled the tuna in the trough. It was easy to shingle thin slices of tomato and eggs over the fish, but things started falling apart when I piled on the onion slices, olives, capers, anchovies, parsley, and marjoram (sweeter and more delicate than oregano or thyme, and distinctly Provençal) and doused the filling in vinaigrette.

I halved the sandwich and did my best to bundle the precariously full halves in plastic wrap before weighting them beneath a Dutch oven for about an hour. But that didn’t stop the olives, capers, and onions from tumbling out when I unwrapped the halves and cut the sandwiches into portions. I needed to make the looser ingredients more cohesive.

First, I borrowed red wine vinegar from the dressing to soak the sliced onion and garlic with a little salt, which mellowed the sharp bite of both alliums and had the bonus effect of wilting the onion and making it more compact. While that mixture sat, I finely chopped the olives, capers, anchovies, and herbs in the food processor and then tossed them with the onion mixture. I divvied it up by packing most of it into the trough beneath the tuna and spreading the rest across the top of the egg slices. These ingredients now stayed mostly contained, and with their briny, salty flavors sandwiching the rest of the filling, each bite tasted balanced.

There was just one problem: Placing the wet olive mixture directly against the bread meant that the crumb, which had been pleasantly moist, was now bordering on sodden.

I looked for ways to curb the amount of free liquid in the filling. One easy fix was to drain the juicy tomatoes on paper towels before placing them in the sandwich. I also combined some olive oil and mustard with the olive mixture so that the mustard could bind up the water from the vinegar and onions. In addition, I made the crumb water‑resistant by brushing the cut surfaces of the baguette with more olive oil. I also decided to toast the baguette before building the sandwich, which would make the exterior more crisp.

When I capped this sandwich with the top of the baguette and sliced it crosswise, the filling stayed put and it was easy to wrap each half into a tidy torpedo. I assembled another Dutch oven “press,” this time with a rimed baking sheet between the pot and the bread to make the setup steadier, and flipped the sandwiches after 30 minutes so that gravity could help evenly distribute the moisture.

The results? Each component of the filling was thoughtful, and the balance of flavors was pitch‑perfect. Brushing oil on the bread kept enough liquid from the filling at bay so that the crumb was moistened but not sodden. And the make-ahead convenience meant that this would be just the thing to serve at backyard parties—yes, a tuna sandwich fit for company—as well as have on hand for busy nights.