The perfect doughnut is fluffy, soft, tender, and moist. The secret ingredient? Potatoes. The starchy tubers absorb moisture, but are stiff enough to hold air.
In the 18th century, German immigrants in Pennsylvania fried up sweet, potato-based doughnuts the day before Ash Wednesday (which kicked of the Lenten season) to help get rid of sugar and fat sitting around the house. In 1937, Yankee magazine published a recipe for "Maine Potato Doughnuts." Yankees were thrifty, and potatoes were cheap, local, and helped make flour stock last longer.
The first doughnut chain in the United States was not Krispy Kreme or Dunkin Donuts, but a Utah-based franchise named Spudnuts. In the 1940s and '50s, the owners took potato-based doughnuts mainstream, opening hundreds of stores. Mr. Spudnut, their proud mascot, made it all the way to outposts in Japan. In 1968, three years into acquisition by a Canadian company, a bad investment destroyed the future of the franchise. Store owners were forced back into independent operation. In 1964, Spudnuts sold an estimated 400,000 doughnuts per day. Today, scattered across the United States, only a few outposts remain standing.