Fifteen or so years ago, by her recollection, a woman named Robin Chapman made a pot roast in her slow cooker. Now known as Mississippi Roast, it would eventually become one of the most popular recipes on the web, an unlikely star with unlikely ingredients, a favorite of the mom-blog set.

Ms. Chapman lives in Ripley, Miss., but she did not call her pot roast Mississippi Roast, not then and not now. She just calls it “roast.” She used beef chuck to make the dish that first time, she told me in an interview, and put a packet of dry ranch-dressing mix on top of the meat, along with a packet of dry “au jus” gravy, a stick of butter and a few pepperoncini. It was an on-the-spot variation of a recipe she had learned from her aunt, which called for packaged Italian dressing. Ms. Chapman wanted something “milder,” she said, so she swapped out the Italian for the ranch.

She set the slow cooker to low and walked away. Some hours later, her family dived into their meal with glee. She has made the roast ever since. And largely unnoticed by food writers and scholars, the recipe has slowly taken on a life of its own.