Making a restaurant last 15 years is a major accomplishment. Making it last that long in South Beach, where people come to reinvent themselves, where change is the status quo even in these rapidly upscaling times, is impressive. And doing so with concept and ownership and decor largely unchanged is miraculous.

You see, even Joe's Stone Crab, that venerable shrine to the shell, underwent a major expansion/redesign a few years back. Not so Osteria del Teatro. This tiny Italian spot, ensconced Manhattan-style in the first floor of an Art Deco theater/turned nightclub at Washington Avenue and Española Way, has stayed the same. Its solid, filling, wonderfully savory Northern Italian cuisine was popular when culinary indulgence was considered glamour, not gluttony. And it is popular even now in a town with at least as many gyms as it has meat markets.

Osteria dazzles with its consistency, with its elegance, with its propensity for taking care of the customer. From the moment when you're warmly greeted at the door, as often as not by owner/maitre d' Dino Pirola, to the clearing-off of dessert plates, you're treated as royal family, service impeccable, attentive without the hint of turnover-inspired hurriedness.

Chef Martin Pérez, Mexican-born, has been chief here for 3 ½ years, sous chef for many more. He executes a menu that's held steady for the long run, although the likelihood of your actually ordering from that menu is slim. The printed menu portrays Osteria as a notch above a rather pricey pasta hut. The daily list of specials hint at something more grand. And an additional list of specials, reported by the skilled server, multiple-ingredient dishes recited as if mantra, indicates gourmet and adventurous leanings. The specials are announced without price, and they are much more expensive than items on the regular menu, but they are quite worthy.

We began with a mix of warm breads, focaccia, sliced country bread and more, served with cold butter. Our first starter was the lone item selected from the standard menu, sautéed wild mushrooms with polenta ($10). This is a mix of wild mushrooms, sautéed in olive oil with fresh herbs, white wine, parsley, garlic. They pair nicely with a mound of soft polenta cooked in a pot; if you prefer the firmer, drier, cornbread-style grilled polenta, you may ask for it. This dish is mild, meaty without meat.

The special starter list yielded a basic, bresaola with arugula ($12). This is a round platter of thinly sliced, cured dry beef with a drizzle of olive oil, Parmesan and lemon. Pirola will un-recommend this dish -- too simple for him, like carpaccios, meat on a plate, yawn. He prefers the fancier dishes.

So let's have one, from the printed list of specials (the menu situation is confusing. Deal with it.). Two giant prawns ($15) are butterflied, cooked and then returned to their shells. Goat cheese is spooned into the fold. Also on the plate is a light citrus sauce -- lemon, butter and white wine -- and a concassé of tomatoes with chives adds color to the picture. Key here is meaty, lush shrimp. Citrus and tomato get playful with the cheese.

There must be 50 entrées here. You can, of course, have spaghetti with tomato sauce. The owner will not like this. Get something that requires creativity. Like Chilean sea bass ($28), spackled with Italian bread crumbs, pan-seared and then baked. It leaves the oven for a bath in Livornese sauce, fresh tomatoes with capers, Kalamata olives, oregano, garlic and basil. Our fat filet was one degree to the right of underdone, which means perfect, moist and juicy yet there with the texture. Go-alongs gave color and flavor -- potato gratin, tiny green beans and a puckery pile of sautéed red cabbage, made spry by vinegar. Excellent dish.

Squid do more than menace tiny sea creatures. They produce a black ink that colors Osteria's homemade taglierini ($26), which does the Halloween thing with an orange curry sauce sporting light cream (one tablespoon, they say, in the entire dish). All is tossed with mixed seafood: shrimp, scallops, squid, baby clams and mussels. This looks heavy, but eat it and see that it's not.

Not so fast with osso bucco with risotto ($29). This is a volcano on a plate, a peak of veal shank on a base of risotto Milanese, flavored with saffron, all doused with red-hot tomato lava. The veal is lightly floured, browned, then braised 2 ½ hours in the oven in a fragrant bath of white wine, veal stock, bay leaf, chopped carrots, onions and celery, fresh tomatoes, basil, rosemary and lemon rind. The meat is plentiful and rich and tender, and the risotto, a salute to calorie, does the trick. Also available with polenta.

Desserts are trotted to the table for viewing. Yearning for something borderline light after this feast, we dug into the almond tulip ($9) with mixed berries and sabayon sauce, served on the side. This is a crunchy, delicious pancake, nutty in flavor almost like a brittle, with a gravy boat of airy, creamy sauce and a fresh mix of berries. Please don't change.