Mention the words “Charlie’s Cafe Exceptionale” to a Twin Cities diner of a certain age, and two words — “potato salad” — will invariably enter the conversation.

Here’s a measure of the salad’s widespread popularity: For years, it generated dozens of annual queries to Restaurant Requests, the Taste section’s long-running column that tracked down restaurant recipes.

When it came to revealing the ins-and-outs behind Charlie’s potato salad, the basic response was, “Never going to happen,” although in 1971 chef George Lisovskis offered some helpful advice.

“It’s really not that difficult,” he said. “It’s like the potato salad you make at home. The difference is that we make our own mayonnaise, using fresh eggs.”

Four years later, the restaurant finally capitulated and submitted a recipe for publication. Turns out, it wasn’t a gigantic secret after all. Although not noted at the time, that 1975 recipe was identical to one that the restaurant had shared with Better Homes & Gardens magazine in 1963.

Here’s where it gets odd. When the recipe was republished in Taste in 1989, Charlie’s owner Louise Saunders picked up the phone and cried “foul.”

“[Saunders] said the time has come to stop using it, ‘Because the recipe is incorrect,’ ” wrote Star Tribune reader representative Lou Gelfand.

But was it? Saunders, then retired — she closed the 49-year-old restaurant in 1982 — insisted that the recipe’s true ingredients were known only to her and to two others. Further, the salad had always been prepared in stages, which prevented employees from devising — and, presumably, stealing — the coveted formula.

Saunders did give her blessing to another slightly altered version, which was published in “Minnesota Eats Out: An Illustrated History” in 2003.

In Saunders’ 2003 obituary, longtime Charlie’s manager David Jensen noted that the recipe’s mayonnaise also relied upon ingredients not available to home cooks, adding that, “Blends of juice from canned fruit might supply the sweetness instead of sugar.”

Yes, the juice from fruit cocktail.

That explains why the Restaurant Requests column was frequently such a juggling act for Taste staffers. Even if they were outwardly sharing their recipes, chefs and restaurateurs weren’t necessarily handing over all of their secrets.