The burgers Jeff Lassen makes behind the low bar of Louis’ Lunch, wearing a white apron stained nearly black on either hip from wiping his gloved hands, follow a simple but unorthodox formula. First he flattens balls of ground beef into patties, lays a slice of onion atop each, then locks six of them in a blackened grate to be slid vertically into one of three tall cast iron broilers; an old Savory radiant gas machine toasts slices of white bread, which he slathers with cheese spread; he sets the charred burger patties atop toast and cheese spread, tops them with a slice of tomato, then caps each with another toast slice and cuts it in half diagonally. Lassen, a block-shouldered Northeasterner, has perfected this string of actions to a dance that is mesmerizing to watch from the bar, but his work is noteworthy for another reason: minus the cheese spread, this is supposedly the same way the very first burger was made, ever, by Lassen’s great grandfather at his food cart in the year 1900 when a hurried customer is said to have yelled, “Slap a meatpuck between two planks and step on it!”

That means every ground beef patty since — Whopper, Big Mac and Double-Double alike — can trace its lineage to this very set of broilers. At least, so the company claims.

It’s surprisingly hard to surmise who in reality first came up with the hamburger. The first signpost to debate may have come during the 1904 World’s Fair in St. Louis, when the New York Tribune first wrote of the hamburger, saying it was “the innovation of a food vendor on the pike.” That bit of vagueness has spawned a bitter debate today about what came before: the Lassen family stakes its claim, as does White Castle (who says it was invented by a German named Otto Kuase in 1891 and brought into modernity by the restaurant’s founder, Walter Anderson), The Seymour Community Historical Society (who says one was put together by one Charlie Nagreen as a meatball between two slices of bread in 1885), and Fletcher Davis, a Texan who sold ground beef between two pieces of Texas Toast and who in fact manned a food stand at the 1904 World’s Fair. Josh Ozersky, the food editor at New York Magazine, derides the idea that Louis’ Lunch created the burger, citing their sandwich’s lack of a bun, which wasn’t invented until the 1920s, in his authoritatively titled book, The Hamburger: A History.

It’s surprisingly hard to surmise who in reality first came up with the hamburger.

All of this is off-putting to the spectator who just wants a bite of the bona fide proto-burger. But a munch at Louis’ in New Haven, Connecticut puts both the empty belly and the jaded mind at ease. Far from being a patty-centric tourist trap, the little brick building on a quiet side street (it moved here in 1975 after it was pushed out of its original location) feels like a neighborhood haunt intruded on by burger-worshiping pilgrims. Lassen and another employees wade through their work happily behind the bar; Lassen slaves away at burgercraft two feet away from where customers await their food; every inch of wood countertop has been heavily scarred and tattooed by customers, which no one seems to mind. The burgers might be called patty melts and are ugly as sin, bleeding medium rare into the white toast, and tasting like fresh beef, which they are. (The secret, Lassen allows carefully when I ask, is five different cuts, ground anew every morning.) Condiments are strictly forbidden; there are myths (that I find hard to believe) about Lassen throwing out Yale students who tried to sneak in ketchup and mustard, which Lassen decries as covering the taste of the meat. There’s a sign that gruffly explains that this establishment is not Burger King, and a wooden circle that features only a ketchup bottle bisected by an angry red slash. As I sit and listen, one customer, an EMT, peppers Lassen with questions about a girl that the EMT has just started dating. Another gossips about the health of a man in a motorcycle accident. Lassen nods, chirps responses, keeps pumping out burgers.

It’s easy to see Lassen as a torch carrier, stubbornly conveying the simple spirit of manning the grill into a modern age filled with burgers that rely on gourmet flourishes or the rich man’s flights of fancy. Louis’ Lunch’s claims might be false, but there remains base pleasure in eating Lassen’s food in front of him as he assembles another batch in the exact same manner as his father, grandfather and great-grandfather. So let the naysayers prickle about dates and facts. The apologist can find the flavors of the original burger here, grounded in reality or otherwise: meat in patty form, bullheaded, simple and delicious.