“Is he cheating on me?” sniffles the woman at the bar, half into her sleeve. She’s talking with the bartender, who, without shifting her eyes away from her friend, sets a menu in front of me.

“Only you know the answer to that, honey – I’ve told you this before. Have another milkshake. You’ll figure it out. And if you don’t, at least you’ll be heartbroken but toasty,” she says, consolingly.

The woman orders The Original ($11), one of BRGR Bar’s selection of booze-infused adult milkshakes, and slurps it percussively through a straw over the course of the next half-hour. Meanwhile, I make my way through an agreeably savory, gorgonzola-laden Oo-Mommy burger ($14.50).

Two months later, I return and order the same drink. I’m having a rough week – maybe not quite as upsetting as a breakup, but still, I could use a little late-autumn invigoration. When I take a sip, I have to squint a little and set my glass down. It is spectacularly sweet, thanks to a hefty dose of New Hampshire maple syrup, and so boozy that the drink tastes flammable. But if I were lovelorn and drowning my feelings in ice cream and alcohol, I doubt I’d complain about the extra bourbon.

For several weeks after the restaurant opened in March, those adult milkshakes were the closest thing to a dessert at BRGR Bar, the Portland outpost of a popular Portsmouth, New Hampshire, restaurant of the same name. Now there’s the Brownie Burger ($10), a caramel and chocolate-sauce-spattered riff on an ice cream sandwich, made from two gluten-free brownie rounds sourced from Gluten Free Territory in Hampton, New Hampshire, and a baseball-sized scoop of peanut-butter ice cream from Shaker Pond Ice Cream in Alfred. It’s more assembly than cooking, but the result is satisfying and large enough to share among two or three people.

Most of BRGR Bar’s dishes are just as amply portioned, even the appetizers. Take the substantial tuna nachos ($13) – a plate heaped high with flour tortilla strips that are fried to order and topped with avocado, red cabbage, cherry tomatoes and cubes of seared tuna, then drizzled with a disappointingly mild wasabi aioli. Or better yet, the Sweet, Hot, and Dirty fries ($8), a cast-iron serving dish overflowing with sweet potato fries topped with two contrasting ingredients: a cantankerously hot Chicago-style hot-pepper relish and a creamy, garlicky cheese sauce that soothes the sting, but just barely.

Executive chef Jon Vogt uses that same trick elsewhere on the menu, but considerably less successfully. In The Godfather Part II ($15) burger, Vogt and his team start with a precisely medium-rare patty that they make from a bespoke grind of Maine Family Farms beef. “It’s chuck, short rib, brisket, with a little more fat added to it to make it juicier,” Vogt said. They top the patty with pre-shaved, flattop-griddled steak meat, a stingy serving of the Chicago hot pepper mix and a glug of the same cheese sauce they use on the sweet potato fries. However, on a burger, with two kinds of meat and a (soggy) brioche bun in the picture, the same ratio of spice to dairy does not work, leaving the burger salty, almost sticky, with barely a prickle of peppery heat.

Tuna nachos are composed of fried-to-order flour tortilla chips topped with avocado, red cabbage, cherry tomatoes, cubes of seared tuna and wasabi aioli.

It’s all the more surprising because BRGR Bar’s best dish may well be its fiery Nashville Hot ($13.50), a crunchy, double-breaded fried chicken sandwich. The kitchen marinates chicken breasts overnight in buttermilk, cayenne pepper, ancho chili and Dijon mustard before coating the meat in a similarly seasoned flour mixture. After frying, the patty practically crackles with high-voltage spice. Yes, it burns a little. That’s the point. But if it gets to be too much, you’ve always got a few slices of housemade dill pickle and dollop of mayonnaise-rich coleslaw to carry you through to the inevitable next bite.

Part of the problem with BRGR Bar is that such gorgeously conceived and executed dishes sit side-by-side with others that are flawed or just plain uninspired. And from the menu alone, it’s hard to tell which is which. Some, like the Just Beet It ($13) – a hamburger with a vegan patty fashioned from shredded beets, topped with a savory feta-yogurt dressing – sound as if they might be winners. But the burger, bound with puréed canned black beans (veggie burger boilerplate), is too moist, with an interior that tastes pasty and underseasoned. It’s a brioche bun filled with purple-gray mediocrity. Vegetarians deserve better.

The Godfather Part II, here served with a side of Parmesan truffle fries, features a beef patty topped with shaved steak, hot-pepper relish and a creamy, garlicky cheese sauce.

Occasionally, even bigger disappointments lie in wait, as my dinner guests and I discovered when we ordered the quinoa salad ($12), a dish that sounded like a perfect seasonal side. We dug through the feta-yogurt-dressed spinach leaves, the cubes of sweet, tender roasted butternut squash and slick, crunchy pepitas. Then we dug some more, finally lifting the bowl up and tilting it to the side, just to make sure we were seeing clearly. Indeed, we were. No quinoa. I suddenly wished I had ordered one of those adult milkshakes because it was, in a word, heartbreaking.

Andrew Ross has written about food in the United Kingdom and in New York, where he co-founded NYCnosh, a food website. He and his work have been featured on Martha Stewart Living Radio and in The New York Times. He is an Internet researcher and higher education consultant. Contact him at:

andrewross.maine@gmail.com

Twitter: @AndrewRossME