The French Dip is a confounding sandwich, at once luxurious – ethereal ribbons of roast beef as genteel as cashmere – and downright messy.

Even the most fastidious diner ends up with jus dripping from fingers, although most don’t seem to mind. Like a juicy burger, the French Dip made its way into the American sandwich pantheon because it requires many napkins.

When 54 Cafe opened in Vandalia, owner Bret Davis felt it necessary to include French Dip on the menu. After all, a something for everyone restaurant needs both burgers and the other all American staple.

It’s just a basic presentation, with thinly sliced meat and perhaps a layer of cheese all that is necessary to start. The accompanying consomme – au jus – transforms the sandwich into something special.

Maybe the verb is too polite. At KC’s Place in Louisiana, where the kitchen has been serving French Dips for two decades, it is more of an explosion than a mere transformation.

Pounds of rustic jerky, the savor of scorched fat clinging to cast iron, the husky tone of beef, rich and mineralic burst from the jus. There’s a hoarse crackle of peppery heat, the bittersweet rasp of garlic, a more delicate herbal flutter.

All of this turns a simple combination of bread, roast beef and melted cheese into an assault – a hearty, wonderful burst of flavors – on the palate.

KC’s owner Karen Johnson won’t reveal everything that is packed into the brooding, shimmering broth waiting in the ramekin served alongside the the sandwich. The jus starts with drippings from prime rib prepared on Saturday evenings. To this is added a beef consomme, garlic and “seasonings.”

Johnson treats the presentation casually. Some restaurants dip the entire sandwich into the jus before bringing it to the table. Others ladle it over the top so broth puddles on the plate. But KC’s keeps the two elements separate.

“A little or a lot — as much as you like,” she said.

But what is the correct way to dip the French Dip? Although the cooks at KC’s warm the roast beef in jus before layering it onto the bread, Johnson prefers to leave the rest to the customer.

“Some don’t like the au jus,” she pointed out. “That’s weird.”

Without the soaking, it’s also just a roast beef sandwich.

Perhaps history can lend a hand. The origin stories of favorite dishes are rarely known and most are riddled with myth. But at least those who care about such things can pretty much pinpoint the French Dip’s debut.

Despite competing claims by another restaurant, research by Jackson Landers for Thrillist in 2016 pegged the sandwich’s beginnings to around 1917 at a Los Angeles restaurant then known as Philippe’s.

How it came about is Landers’ major find – although he only had to look through a newspaper to make the discovery.

One story had chef Philippe Mathieu accidentally dropping bread for a roast beef sandwich into a pan of broth. Another told of a man with a sore tooth asking for softer bread. A bath in the pan was the only thing the chef could think of. And there are versions.

In each there is beef involved and the entire loaf ends up dipped. In a 1951 Los Angeles Times interview with Mathieu himself, the chef revealed that it started with roast pork rather than beef. And that a customer who ordered a sandwich saw a pan full of gravy and asked that it be dipped.

So no smothering, just a simple touch in the liquid. Johnson may be on the right track. It’s the customer’s choice.

“We just give them a bowl of au jus,” she said.