Mustard Museum in Middleton, Wisconsin

Mustard Museum's Barry Levenson says, "Welcome to my midlife crisis." (Curt Brown/Minneapolis Star Tribune/MCT / November 22, 2011)

MIDDELTON, Wis. — Barry Levenson stopped in his hotel hallway, looked both ways, then pocketed a tiny jar of room service mustard on a discarded tray.

Never mind that as an assistant Wisconsin attorney general 25 years ago, he was about to scale his profession's pinnacle and argue in front of the U.S. Supreme Court.

That lucky mustard jar — believed to be the only condiment to ever appear before the high court — has gone from Levenson's left pocket to a glass display case at the National Mustard Museum.

"How poetic," the placard reads, "that a jar of mustard would stand before a bench that once included Justices Felix Frankfurter and Warren Burger."

The museum, Levenson's goofy, tongue-in-cheek shrine to his beloved mustard, sits in a two-story brick building in Middleton, on the outskirts of Madison. There you'll find not only 5,400 different kinds of mustard, but you'll probably bump into Levenson, a Woody Allenesque nebbish with a slightly demented grin and a fully demented hobby.

"I could have done anything sane, but I decided to go off the deep end and collect mustard," he said, shrugging. "Welcome to my midlife crisis."

The National Mustard Museum resides in the basement; a tasting room and mustard shop occupy the upstairs. For a suggested $5 fee, you can wander around downstairs and check out mustards from 79 countries.

"Azerbaijan to Zimbabwe," Levenson boasts.

There's a passion-fruit/habanero mustard from Hawaii, a caramelized onion version from Maine and the reigning world champ, a ginger-curry concoction from Benicia, Calif.

Every spring, the Levensons round up foodies, chefs and dozens of other mustard tasters and judge the best in myriad categories ranging from honey to horseradish. Last year, the awards festival moved from Napa, Calif., to Middleton.

"There was mustard bowling and all kinds of activities," said Sara Leverson,who works at the Neena clothing boutique across the street from the museum. "I asked for ketchup at the hot dog stand and, oh, the look I got."

Levenson pointed her to a sign on the stand that informed everyone that mustard was free. Ketchup cost $10.

As much as Levenson loves mustard, he despises ketchup and mayo.

Down in his basement museum, right near the "Mustard Piece Theatre" that shows documentaries and old advertising clips, we found Levenson.

He grew up in Worcester, Mass., and came to Wisconsin in 1970 to practice law after experiencing some cold spiritual feet. He'd been accepted to the Hebrew Union College rabbinical school in Cincinnati and even worked as interim education director at Temple Israel in Minneapolis "for about 20 minutes" before ditching organized religion for law. He turned 63 in December.

He points out that at the Supreme Court mustard case, he won his argument 5-4, allowing authorities with reliable tips to search, without warrants, for weapons in the homes of people who are on probation.

"I think they got it wrong, but I was working as a prosecutor and they agreed with my argument," he said.

But why leave a successful law practice to collect mustard, with a business card that calls him a curator and Chief Mustard Officer?

It all started with baseball. Levenson grew up a die-hard Boston Red Sox fan. When the Bosox blew the 1986 World Series, Levenson said, he became despondent.