As we strolled through the elegant old streets of Hamburg, with enchanting red-brick warehouses on one side of us and the striking, glass-topped Elbe Philharmonic Hall rising in the distance, native Helmut Moller talked about the city’s history. He oozed civic pride and self-confidence – particularly when he made his boldest claim of the evening: “The hamburger,” he said, “comes from Hamburg.”

It sounded like one of the most “well, duh” statements I’d ever heard. After all, the frankfurter really was born in Frankfurt. But as I was about to learn, the burger’s past is a little more – well, messy.

Hamburgers may be most associated with the United States, where these days, you can find a version on the menu of almost any upscale restaurant priced at more than $20 and stuffed with foie gras or topped with truffles. But Europe is going through its own burger obsession. A recent Wall Street Journal article revealed that a dedicated hamburger eater can now find a tasty burger in nearly every big European city.

Could this mean the hamburger has finally come full circle – that after a grand culinary tour of the New World, this hot sandwich has returned home to Europeans, who are the rightful heirs to the hamburger throne?

I intended to find out – to do a little digging and learn once and for all where the hamburger began. What Moller, a friend of a friend, was referring to when he spoke of the burger’s origins was the local, centuries-old hot pork sandwich called the rundstück warm – which is a low-German translation of “round piece warm”, referring to the sandwich’s round bun-like bread. When Moller first said the words, they seeped from his mouth like goopy melted cheese. In fact, I didn’t understand him, and when I asked him to repeat them, he appeared to be losing patience with me. “Roondshtook vahrm,” he said very slowly, sounding it out. “It’s the ancestor of the hamburger. Go find it and you can decide.”

Hamburg is home to a handful of restaurants that serve this possible proto-burger. Moller scrawled a few names down for me. One is Krameramtstuben, which all the pilsners in the world won’t help you pronounce if you don’t speak German. The place has been open since 1718, but when I got there I found it was closed for the day.

So I went to the next one on Moller’s list: Oberhafen Kantine, seven decades old, set in a leaning house on the port below elevated railroad tracks. I walked in to find a couple of bearded fellows chatting with an inked-up female server over pints of lager. She looked at me expectantly.

“Rundstück warm?” I said, trying my hardest to twist my tongue in a way that would have pleased Moller.

She nodded and barked something at the chef. A few minutes later, she placed it in front of me: the rundstück warm, which, depending on who you ask, could be the ur-burger, the modern’s hamburger’s forbearer whose DNA permeates every Big Mac and Whopper the world over. Before I could dig in, owner Sebastian Libbert wandered over. I couldn’t help but interrogate him.

“The rundstück warm has roots as a snack for dock workers,” he said. “But really it’s a leftover, something you eat on Monday as the remains from the usual Sunday pork roast.”

The rundstück warm consists of day-old pork topped with either beet root, pickles, tomato slices, or even chives. It’s sandwiched between two round buns and doused with pork gravy.

“It should normally only have a bottom bun,” Libbert said. “This is a modernized version.”

Just so I could try a variety of types – if such diversity existed – I’d been hoping to find a chef or restaurant in Hamburg that made an elevated version of the rundstück warm, perhaps with pork belly and topped with foie gras between a potato roll or ciabatta bread. My search proved fruitless. Apparently adding a top bun is about as “haute” as I was going to find in Hamburg.

But the question remained: Does the hamburger descend from the rundstück warm?

Maybe. According to some historians, the rundstück warm originated in the 17th Century, when Hamburg bakeries began making a round roll. Soon after, the roll began being served with leftover pork and gravy at lunchtime on Mondays – and with that, the rundstück warm was born.

If this culinary development had occurred anywhere else, the concoction probably wouldn’t have made the leap across the Atlantic. But Hamburg has long been an important port city connecting Europe to the United States. At some point in the 18th Century, German immigrants set up food stalls in New York City advertising “Steak Cooked in the Hamburg Style” to German sailors and newly arrived German immigrants. The stalls were mysteriously serving beef, not pork, placed between two halves of a round bun.

I picked up the rundstück warm and took a bite. It tasted exactly as I expected: a porky mouthful aided by gravy. The chives, sprinkled on top of the pork, added another flavor strata as well as a bit of a crunch. I could certainly see the connection.

I asked Libbert if he thought the rundstück warm was the original hamburger.

“Yes, probably,” he said with a shrug.

But food historians disagree on the modern burger’s origins. While some believe the hamburger does descend from the rundstück warm, others contend it originated elsewhere. Beef patties date as far back as Roman times. Investigate when beef patties were placed between slices of bread and you find some historians pointing not to German food stalls in New York but a county fair in Wisconsin.

In the late 1800s, Charles Nagreen was selling Hamburg steaks – essentially a burger minus the bun, which some trace back to Hamburg – at the Outagamie County Fair in Wisconsin. Sales were weak because eating a piece of meat on the go was a messy affair. But in 1885, he had an epiphany: If he put the meat between two pieces of bread, people could walk around holding it. And that development, some say, created the hamburger.

Similar tales from the same era credit burger innovators in Ohio, Texas, Connecticut and beyond. Unfortunately, there’s no conclusive evidence of exactly where or how the burger began. One thing is fairly certain, though: Nearly all stories begin with the protagonist using a “Hamburg steak,” which means the city of Hamburg has – and will always be – associated with the hot sandwich.

If the rundstück warm really is the precursor to the modern hamburger, it feels more like a great uncle than a grandfather. I think of the way musical historians draw a line from Chuck Berry through the Beatles to Foo Fighters. There’s not a direct A-to-B lineage but more of a zigzagging route with a couple of twists erased and lost to history.

Regardless, after sinking my teeth into the sandwich, I was sure of one thing: Whether it’s the grandfather of the contemporary hamburger or not, the rundstück warm is tasty enough to try when you find yourself hungry in Hamburg.