If you haven’t been to Frontier in a while, you may be taken aback when you walk in.

The surprise is a little like encountering a young person you haven’t seen in a while who’s now on the far side of adolescence. Still located in a former mill space at Fort Andross and still presenting films and performances in a small attached theater, Frontier is all grown up. And gorgeous.

The place has been expanded and reconfigured. The design still mixes contemporary industrial and vintage rustic styles. But a 12-seat bar replaces the old ordering counter, and high-top tables fill the former entrance space. Remaining is the row of hefty communal wood benches and tables made from reclaimed wood, and the armchair area. On the walls hang changing exhibits that often resonate with the theater’s programs.

Artsy lighting warms the floor-to-ceiling wood, and gives the space a soft radiance at night. Outside enormous windows, the Androscoggin River rushes over the dam. By day, catch the bald eagle soaring overhead; at night, the glitter on the bridge fools you into thinking you’re in a metropolis.

The eatery now has a full kitchen, which means it can dish up complete dinners as opposed to just salads, soups, sandwiches and its trademark market plates. No more carrying numbers to your seats — table service has arrived too.

We dined at Frontier six weeks after its mid-December reopening, and were happy to find a bustling house and a forward-thinking and globally inspired menu that wasn’t overly ambitious or expensive. The unfussy yet intelligent vibe of the old cafe seemed to have transferred to the new iteration.

A flavor-rich and seafood-laden clam chowder ($6) was an auspicious start to our meal. Another bowl of bliss followed: Curried PEI mussels served with lemongrass, kaffir lime leaf and spices in a coconut milk base. The bivalves were steamed to optimal doneness, and the not-too-overbearing sauce was a mingling of unusual flavors that enhanced the seafood and begged to be sopped up with the warm nan slices ($11).

The appetizer bust was the trio of overdone Kobe beef sliders ($9). Too bad, because the fixings were sharp and distinctive: Rosemary mayo, wasabi mustard and curry ketchup.

A frisee and endive salad with roasted Brussels sprouts and toasted pecans won us over again. The sprouts were sweet on their own; the champagne vinaigrette was well-balanced and bright. A horiatiki salad of spinach, feta, cucumbers, kalamata olives and grape tomatoes with a homemade tahini dressing was fine, just less impressive in contrast (each $6).

We happened to hit the restaurant during a Saturday-night pre-concert crush, so entrees took some time to get to our table, but not uncomfortably so. Our server, genial and skilled, explained and apologized for the delay.

The entree winner was tender and lean pancetta-wrapped pork loin medallions with red onion marmalade, a silky potato and parsnip puree, and Brussels sprouts — a dynamite platter worthy of any chef. It surpassed similar dishes I’ve tasted in the last few months, and was an excellent value at $16.

A haddock, fennel and chorizo stew in a saffron tomato broth arrived in its cooking pan, its large filet of poached fish central to a broth studded with slivers of the sausage, which overpowered the mild fish (no surprise, and not a complaint). An attractive dish served with rice and priced at $17, the stew took a close second place.

The curry-and-stout-braised short rib bore an earthy flavor, longer on stout than curry, yet the texture was a tad dry ($20). A side of blue cheese grits, an excellent if unusual pairing, added a smooth and welcome tang to this hearty plate.

Fish tacos ($14.50) simply needed more fish in the hard blue-corn shells; three cubes of fried, rice-battered fish weren’t enough. I’d also prefer soft wrappers to build the tacos with the splendid accoutrements that accompanied them — tomatillo salsa, cilantro creme fraiche, pickled red cabbage, and carrot with mint and lime.

When it came to the final course, Frontier nailed the details: Strong, fresh coffee and herb tea from house-wrapped bags of leaves, infused at our table. A warm blueberry crisp held flavors of nutmeg and coconut in a crispy, grainy top layer, with about an equal part of wild blueberries beneath ($7).

Crinkly flakes coated a warm, savory-sweet “five-spice” fried banana placed on caramel sauce drizzle and served with green tea gelato ($6), our second dessert. This was interesting, but not heaven-sent.

From its start five years ago, Frontier has emphasized Maine purveyors, even choosing local pottery as its dishware. And while chef Jason Putnam leaves certain foods to other specialists — several of the dessert offerings are from Gelato Fiasco down the block, and the veggie burger is Blue Mango’s of Portland, for instance — Frontier nevertheless turns out plenty of its own high-quality, innovative food and drink, and serves it graciously in a stylish atmosphere.

Welcome to the new adult on the block. 

Nancy Heiser is a freelance writer. She can be reached www.nancyheiser.com