The burger: Those in search of a testament to the goodness of the All American Double Patty Cheese Burger at Union Rooftop, look no further. "It's the reason I've gained 10 pounds," said chef Stewart Woodman with a laugh. "There's just something about it that's so satisfying. It just kind of hits the spot."

Agreed. If I found myself in the building as frequently as Woodman — he also oversees the first-floor Workshop at Union, which features its own spotlight-worthy burger — I'd be sorely tempted to knock one of these things back on a frequent if not daily basis.

When it arrived at the table, my first thought ran to Alfred Portale, leader of the Tall Food movement in the early 1990s. This is one bruiser of a burger, built with a pair of stacked 4-oz. patties (yes, that's a half-pound) that cannot be described as thin. After taking a few moments to study its heft, I couldn't determine a polite way to pick it up, so I reached for my knife and fork.

One taste, and my thought process turned to In-N-Out, the beloved California-based burger chain that really needs to expand into the Minnesota market. Later, talking to Woodman, I discovered that my hunch wasn't off. Well, for the second observation, anyway; we never discussed Portale. But In-N-Out? Sure.

"For lack of a better comparison, it's drawn from the Double Double," said Woodman, referring to the chain's top-selling burger.

Yet Union Rooftop's "Double" isn't a blatant attempt at a copy, it's more of an affectionate homage. Here's the process: The patties are grilled on a flattop ("That's the only way to do it," said Woodman), and they're composed of a lightly seasoned (just salt and pepper) and indulgently fatty sirloin blend, one that follows a 70 percent meat/30 percent fat makeup.

The combination certainly makes for a juicy burger experience ("The fat kind of melts on the flattop, it almost steams, to a certain extent," said Woodman), even when cooked to a near-medium, with the outer edges peppered with a gently crunchy char. It's a melt-in-your-mouth kind of patty. Sorry, patties.

The burger's uncomplicated embellishments also evoke In-N-Out. The well-constructed bun (from Main Street Bakery) is all golden goodness. Shredded lettuce (layered under the bottom patty, a la In-N-Out) adds crunch, a hint of red onion tickles the taste buds and a (dreary, it must be said) tomato slice contributes color (maybe, during tomato season, it'll add flavor, and juice). Oh, and I almost forgot: mayonnaise. Delicious mayonnaise.

"It's gotta have mayo," said Woodman, and he's right. He uses Kewpie, the ultra-creamy, umami-laden mayonnaise from Japan, and it adds a welcome punch. I immediately made a mental note to add a bottle to my grocery shopping list.

As for the cheese, it's American, all the way, and plenty of it, noticeably salty and melting in all the right places, clinging to the sizzling beef. "It's the quintessential cheese for a burger," said Woodman. "It's not the only cheese. I love blue cheese on a burger. But the question is, 'How do I want to treat my favorite burger? In the context of this double stack, American is the perfect partner."

What a coincidence, as this is a close-to-perfect burger.

Price: $13.95 and available at lunch, dinner and Sunday brunch.

Fries: Included, and fine in a does-the-trick kind of way.

Location, location, location: Take a first-timer to the instant mood elevator that is Union Rooftop and you'll probably hear the same one-word evaluation that I usually do, and that's "wow." The drama is all in the roof, a 28-foot-high glass-and-steel barrel vault. It's a greenhouse in the sky, rain or snow or shine, with downtown's skyscrapers surrounding like so many sequoias. It's not unlike encountering a little slice of Centre Pompidou, minus, of course, Paris. But to say that there's nothing else like it in the Twin Cities is an understatement. And although it's a summer-into-perpetuity kind of place, the rooftop actually changes with the seasons, and at the push of a button. When weather permits, someone somewhere flips a switch and, 15 minutes later, the roof, having folded like a telescope, is discreetly dispatched to storage. Ta-da: You're now seated in downtown's best-looking open-air patio. Talk about a tailor-made setting for that burger. "It's what I want to eat in that environment," said Woodman. "I haven't convinced them on my whole pitchers-of-margaritas idea. Yet."

Address book: 731 Hennepin Av. S., Mpls., 612-455-6690. Open 11 a.m. to 10 p.m. Mon.-Thu., 11 a.m. to 11 p.m. Fri., 3 p.m. to 11 p.m. Sat., 8 a.m. to 10 p.m. Sun.

Talk to me: Do you have a favorite burger? Share the details at rick.nelson@startribune.com