Though it’s only been open since October, Downcity’s sister restaurant, Oak, is the happening thing on upper Hope Street. Doors open at five for dinner, and on a recent Saturday night when we visited, half a dozen tables were filled by 5:05 (no reservations for small parties). More than a dozen people were packed into a line and at the small bar, waiting for a table, when we left around 6:45. So be forewarned.

What could inspire such popularity? The answers include great food, carefully prepared; a well thought-out wine list; and friendly and helpful service. What more could you ask for? Well, maybe a coat rack, but more about that later.

On these shivery nights, the atmosphere at Oak is welcoming and warming in several ways: the Mediterranean red in the walls, with large wooden cutouts of oak leaves; the brown bistro paper over burgundy linens (not as cold as stark white); the feeling of conviviality among the diners, many of whom seem to be repeat customers and/or close neighbors. Even the sound level of so many bodies in a relatively small space is not a problem, since music does not compete with the voices, and the ceilings are high enough to keep the acoustics working well.

A previous visit at lunchtime confirmed the loyalty of local diners, and our salad choices — classic Caesar with grilled chicken, and Boston Bibb with grilled asparagus, plum tomatoes, goat cheese, and shallot crisps with mandarin vinaigrette — were quite delicious. These salads are also available in the evening, along with a baby spinach one with smoked bacon, mesclun with a goat cheese crouton, and an antipasto ($9), which is what we picked, along with the polenta fries ($6), to get us underway.

The polenta fries are thicker than steak fries, covered with, as the menu describes it, a "zippy marinara" and a bit of mascarpone. We loved them. We also enjoyed the antipasto, with its generous portions of grilled asparagus and portobello slices, red onions, roasted red peppers, marinated artichoke hearts, and fresh mozzarella, all on a bed of crisp mesclun greens.

Both of these Italian-themed starters led me to the pastas on Oak’s menu: lobster ravioli with grilled shrimp; roasted pepper and goat cheese agnolotti; potato gnocchi; penne with marinara, grilled chicken, or shrimp; pasta Bolognese (tomato sauce with braised veal and Angus beef); and my choice: grilled vegetable and basil ravioli ($12). Our perky waitress Kerri mentioned that these ravioli are her favorite. The eight ravioli were tossed with primavera vegetables — zucchini, carrots, peppers, and onions — and topped with a dreamy pesto cream sauce.

Bill was studying the entrees, ranging from chicken with artichokes and olives or roast duck in a balsamic and cherry reduction to beef tournedos or grilled jerk pork tenderloin ($14), which is what he got. He could barely contain himself over the extremely tender cut of the pork, its crusty edges with that bite of jerk rub and the sweet and spicy apple chutney that surrounded it. He also was quite taken with the mound of roasted mashed sweet potatoes and a nice side of steamed green beans.

We both tried, in our professional way, to push back our main courses half way through to leave room for co-owner Anthony Salemme’s desserts ($6 each), which change nightly. I was leaning toward the pina colada torte, which Kerri also liked, but Bill’s heart is always with chocolate, so the Black Forest bread pudding beckoned. There was also a vanilla bean flan, a Milano tiramisu, and "Bahama’s Fudge Pie."

After much deliberation, we ended up with an orange chocolate chunk torte, with fresh whipped cream to add to its richness. The taste of orange came through in the light-colored cake, while the chunks of chocolate were in the filling and the frosting. This was one of those cases where — throwing all manner of health precautions to the wing — I had to race to keep up with Bill or face not having my fair share of this dessert. It was that good.

Co-owner Paul Shire’s wife, Susan, is the manager at Oak, and she is responsible for the restaurant’s wine selection and unusual cocktails. We chose a chardonnay from Monterey, based partly on our sentimental attachment to a spot we called home for three years. Other wines are from the Napa Valley, Australia, New Zealand, and the Continent.

This brings me full circle to the lack of coat racks in so many American restaurants, even those with an upscale flair, such as Oak. Just back from a sojourn in Europe, Bill and I very much appreciated the ubiquity of these racks (or hooks) in even the tiniest eating spots in Venice, Munich, or Cologne. May we make a modest request to local restaurants to keep customers’ outerwear in mind when designing a new place?

Nonetheless, even with coats on chair backs, you’ll love the food, drink and service at this new neighborhood favorite.