(THE WASHINGTON POST) - Whether you Are road tripping, picnicking or feeding the soccer team after a game, a crowd-pleasing sandwich is a winning concept. But the bumps along the way are fearsome. We have all had bad sandwiches: The bread is soggy. The fillings and condiments slip and slide. And discrete flavours often become murky and indistinguishable if a sandwich sits around too long.

It does not have to be this way. Pan bagnat, literally "bathed bread," is designed for just the kind of sitting around that would ruin a lesser combination. Leave it to the French to fill a loaf of crusty bread with tuna or anchovies, peppers, olives and more, and then bathe the sandwich in vinaigrette and wrap it up, letting its flavors develop over several hours. There is only one way this procedure achieves a glorious, sturdy-not-slimy sandwich: the bread. A baguette with a crackly shell of crust is imperative. Soft bread has no place here.

I began to ponder a variation on the traditional pan bagnat using charcuterie, vegetables and cheese. An antipasti cart spied at a nondescript restaurant in Upstate New York sealed the deal. By adding vegetables in the form of eggplant caponata, bookending the meaty filling, I made sure there was no chance of a slippery mess. The sandwich pulled together like the long lost Italian cousin of the original French.

Caponata is more than a sandwich condiment. It is a relish, a side dish, a salad, a carry-me-to-work lunch with a hunk of bread and a wedge of cheese, and a celebration of agrodolce, that delicate balance of sweet and sour. Eggplant caponata recipes vary regionally: Some have nuts, others sport raisins, but I prefer to let the eggplant shine with not much more than tomatoes and a smattering of salty additions.

Buy big, unblemished, taut-skinned purple eggplant, as fresh as possible. Fresher means less potential for bitterness. While the ingredient list may seem long, it is more a pinch of this and a scoop of that, with most of them likely to be lurking in the pantry. Substitute at will: If there are no capers around, add more olives. Change up the vinegar to use that bottle you acquired on vacation. This is a bold condiment party that sings in sweet, salty, acidic tones.

One medium eggplant makes a good helping of caponata, about twice what is needed for the sandwich. Whizz half in the blender to make a spreadable condiment. Save the other half in its chunky form. Caponata has a long shelf life, at least a week, and refreshes with a wee drizzle of vinegar and a tiny sprinkling of sugar. It is possible to purchase jarred caponata, but freshly made has a crunch (from celery) unlike any in the jar.

Let us get back to the sandwich. Scoop out and form a trench down the center of each side of the bread, and what goes inside will stay put. Arrange the fillings so the flavours blend yet assert themselves as individuals.

A pan bagnat benefits from a long marination before slicing for serving. Although this sandwich is often pressed, the Italian version is better left to mature without anything to weigh it down. Start the process with a plastic-wrap lined counter, open the bread like a book and set it atop that wrap, fill the trenches, and construct the sandwich. Once done, snugly wrap the baguette with the flavours trapped inside, and refrigerate overnight or carry it away in a picnic basket. By the time you have settled next to a stream and unfurled the blanket, the sandwich will be ready.

I am partial to slicing the sandwich on the diagonal into two-inch segments using a serrated bread knife. Keep the sandwich wrapped while slicing and then peel away the plastic and tuck the slice inside a picnic-perfect absorbent napkin. Serve with a light, bright red wine, then lie back and stare at the clouds.

'Antipasti' Pan Bagnat With Eggplant Caponata

12 servings

MAKE AHEAD: The caponata needs to sit for two to three hours at room temperature before serving or storing; it can be refrigerated up to 1 week in advance. Leftovers can be used with grilled meats and fish. If you make it ahead, refresh the piquant agrodolce with a splash of vinegar and a pinch of salt before serving. Assemble and tightly wrap this sandwich the night before or at least eight hours in advance.

INGREDIENTS

For the caponata

1/2 cup olive oil

450g Italian eggplant, peeled and cut into 1.2cm cubes

1 tsp kosher salt

1 medium red onion, cut into 1.2cm dice (about 1 cup)

3 celery ribs, halved and cut into 1.2cm dice (about 3/4 cup)

3/4 cup canned no-salt-added crushed tomatoes

1/2 cup pitted Sicilian or other lightly cured green olives, chopped

1/4 cup capers, rinsed and drained

2 Tbsps sugar, or more as needed

2 Tbsps red wine vinegar, or more as needed

1/4 cup torn basil leaves

For the sandwich

1 baguette (340g to 400g )

113g hard salami (12 slices)

56g sopressata (12 slices)

56g prosciutto (8 slices)

170g sliced provolone (8 slices), each cut in half

METHOD

For the caponata:

1. Heat 1/4 cup of the oil in a heavy, deep skillet over medium-high heat. Once the oil begins to shimmer, add half of the eggplant cubes. Cook for about 8 minutes, until lightly golden brown tender, then transfer to a large bowl. Season with some of the salt.

2. Add 2 tablespoons of the oil to the skillet, then add the remaining eggplant and cook it the same way (over medium-high heat). Scrape the eggplant and any oil in the pan into the same bowl. Season with the remaining salt and toss to coat.

3. Heat the remaining 2 tablespoons of oil over medium heat in the same pan. Stir in the onion and cook for 6 to 8 minutes, until translucent, then stir in the celery and cook for 2 or 3 minutes, just until it is crisp-tender.

4. Add the tomatoes, olives and capers to the onion in the skillet, then return all the eggplant cubes and their oil to the pan. Once the mixture is heated through and a few bubbles appear on the surface, make a well at the center and add the sugar and vinegar. Stir until the sugar has dissolved, then blend that into the eggplant mixture; this is your caponata. Taste; the flavour should be assertively sour and sweet. Add a dash more sugar or vinegar, as needed. Stir in the basil leaves. The yield is about 4 1/4 cups; you will need 2 cups' worth for the sandwich.

5. Spoon the caponata into a bowl, drape with a clean kitchen towel and let the mixture cool and the flavours meld over the next 2 to 3 hours. Remove the towel and cover snugly with plastic wrap; refrigerate until ready to use. Bring to room temperature before serving.

For the sandwich:

1. Put 2 cups of the caponata into a blender or food processor. Pulse to the consistency of a meaty spaghetti sauce (not completely smooth).

2. Cut the baguette in half lengthwise; tear out the soft insides of the baguette to accommodate the sandwich fillings. This will keep the sandwich from sliding apart. Generously fill the top and bottom hollows with the blended caponata.

3. Arrange slices of salami, sopressata and prosciutto on the bottom half of the baguette. Build a layer with the cheese half-slices. Repeat. Cover the meats and cheese with the remaining blended caponata, then place the upper half of the baguette on top to form the sandwich. Wrap it snugly with plastic wrap and refrigerate for at least 8 hours, and up to overnight.

4. To serve, cut the sandwich (still wrapped) crosswise into 12 equal portions.

Nutrition | Per serving (using 2 cups caponata): 240 calories, 11g protein, 17g carbohydrates, 14g fat, 5g saturated fat, 25mg cholesterol, 700mg sodium, 1g dietary fiber, 3g sugar