The Restaurant Requests column’s most-requested recipe was the potato salad at Charlie’s Cafe Exceptionale in downtown Minneapolis, and it demonstrated the column’s never-ending tug-of-war between readers’ needs for clearly-written recipes and chefs’ desire to maintain trade secrets.

Queries for the salad came early, and often. Within the first few months of the column’s debut, more than a dozen readers wrote in asking for Charlie’s most talked-about appetizer.

“This may be a challenge,” wrote Clementine Michael of Minneapolis, in what might have been the understatement of 1971. The restaurant’s reply was basically, “Never going to happen,” although chef George Lisovskis offered some helpful advice.

“It’s really not that difficult,” he replied. “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 was identical to one that they’d shared with Better Homes & Gardens magazine in 1963.

Oddly, when the recipe was republished in “Requests” in 1989 — part of a Taste 20th anniversary issue — 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” (Minnesota Historical Society Press) 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. Another example of why the Restaurant Requests column was such a juggling act. Even if they were outwardly sharing their recipes, chefs and restaurateurs weren’t necessarily handing over all of their secrets.