Of the thousands of people who drive by Robke’s Country Inn each day, some might guess that it’s a German place and one that has perhaps weathered many storms. The low-slung, oddly angled building on Route 25A in Northport has a vaguely Bavarian facade and the feel of another era.

While plenty of sausage is served here, it isn’t bratwurst. Inside its string of tavern-like dining rooms, Robke’s is a classic Italian osteria with heaping portions that has garnered a passionate following since 1978, when Bronx chef Louis Selvaggio took over the place from previous owner Ernest Robke, and began importing provisions and recipes from Arthur Avenue.

The cash-only Robke’s has not only survived for 39 years, an eternity in the restaurant world, but is still flourishing. Arrive at 8 on Saturday night, and it feels like the rest of the world has descended on the place, too: The tiny parking lot is full, and the foyer is jammed with waiting couples. It’s four deep at the bar as the hostess manages pages of names and servers squeeze by the standing-room crowd with plates held high. The clamor is deafening.

Partly responsible for these recent swarms is Selvaggio’s son, Louis Selvaggio Jr. (called Louis Sel for short, and who manages the front of the house). Months ago, he posted a picture of Robke’s fried mozzarella tower — a stack of golden-brown slabs of cheese, topped with sauce — to Instagram; it went viral and garnered national attention. Soon, even more people wanted in on Robke’s generous plates, heavy pours and frenetic, friendly charms.

It takes wherewithal to arrive here at prime dinner time. It’s not unheard of to wait 30 minutes or more, even with a reservation. You can while that time by grabbing a drink at the long, jammed bar, though if you’re not a regular, making eye contact with a bartender is its own sport. (Don’t bother asking for a cocktail or wine list — neither exists).

Once at a hard-won table, a dish of crumbled Parmesan, olives and soppressata will be plunked down, as will a basket of crusty Italian bread. These will steady you during the difficult decision-making ahead: In addition to the regular menu, there are board specials and even more specials that your server will recite as if sharing a secret.

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Hits and misfires lurk on both menus. Robke’s sells plenty of that mozzarella tower, but it’s more a gooey novelty than anything. Eclipsing it is the crisp, clean, featherlight fried calamari, with Robke’s excellent marinara, or a side dish of fork-tender meatballs. The Caesar salad is strangely sweet, best passed over in favor of pasta: A subtly creamy bucatini amatriciana punctuated by chunky tomatoes and just enough fat, or a velvety “secret” veal sauce slathered on pappardelle so wide you almost write a love letter on each ribbon. Conversely, cavatelli with eggplant and mozzarella, a special one night, was chewy and flavorless. A linguine with clam sauce loaded with meaty, fresh clams — plus whole cloves of garlic — suffered from grit, as did a baked-clams appetizer.

Other seafood dishes are sublime, however, such as a red-snapper al forno, a top-breaded fillet baked to suppleness and anointed with buttery cherry tomatoes, or orange roughy oreganata, delicate fillets under a sheath of nut-brown crunch.

Main-course territory can be uneven. Chicken scarpariello is offered both on the bone or off; we took it on, and while the bird was just shy of dry, the dish’s heat was unbridled, and its sauce too vinegary. A lobster-shrimp risotto special arrived loaded with meat, but the dish’s texture was more akin to a tomato-rice soup. Another special, osso buco, suffered from being both overcooked and then served lukewarm, so that its sauce had begun to coagulate.

On that same busy night, lukewarm dishes appeared at every course, rendering the soft ricotta inside an eggplant rollatini gummy, for instance. But redemption came via Robke’s excellent cheeseburger, with delectable outside char and oceans of umami within. Robke’s roughed-edged fries could be habit forming.

When Robke’s is humming but not overrun, it’s a place you can join in the rollicking vibe and indulge in ginormous portions. To dip your toes in its waters, consider visiting at lunch, or long before the dinnertime rush.