Although the doors don’t open until 11 a.m., the parking lot is already filling up on a Friday morning at Lakeview Lutheran Church in Madison, Wisconsin. Inside, volunteers busily set tables, stir boiling pots and dish out plates of food they’ve been planning and preparing for weeks. Outside, pink-cheeked diners decked in Nordic sweaters head up the steps, eager for their annual taste of lye-soaked cod drenched in melted butter.

“I like lutefisk! It tastes good to me,” says Nelson Walstead with a laugh. Walstead, a Norwegian-American, is the chief organizer of Lakeview Lutheran’s annual lutefisk dinner. “It makes me feel good to know we are keeping the tradition alive, and that we’re passing this on to the next generation,” he says.

It seems only natural that the descendants of the Vikings, perhaps history’s greatest tough guys, would celebrate a food prepared with a caustic and highly dangerous substance. Lutefisk—codfish (fisk) preserved in lye (lut)—is both a delicacy and a tradition among Scandinavian-Americans, who serve the chemical-soaked, gelatinous fish with a warm and friendly smile. Lutefisk, or lutfisk in Swedish, is a traditional dish in Norway, Sweden, and parts of Finland.

But today, Scandinavians rarely eat lutefisk. Far more lutefisk is consumed in the United States, much of it in church and lodge basements. In fact, the self-proclaimed “lutefisk capital of the world” isn’t in Norway but in Madison, Minnesota, where a fiberglass codfish named “Lou T. Fisk” welcomes visitors to this lye-fish loving town. The lutefisk dinner is an annual fall and winter tradition at scores of Lutheran churches and Nordic fraternal groups throughout the Upper Midwest and Pacific Northwest or anywhere with a large Scandinavian-American population. Strangely, these children of immigrants celebrate a tradition that connects them to their ancestral home, even as many Scandinavians have moved on.

“These dinners represent impor...