To say that Diamond Head Grill has become an Italian restaurant may give an altogether false and unfortunate impression.

Yes, chef Eric Sakai's primary influences are regional and contemporary Italian, from his work at critically acclaimed Aquarelle and Rubicon in San Francisco. But banish all thoughts of red sauce or meatballs.

Sakai, 24, is a Hawai'i Kai kid who, at the suggestion of his mentor, Alan Takasaki of Le Bistro, earned his culinary degree at the Culinary Institute of America. Now, back in the Islands six months, he is doing something at Diamond Head Grill that no one else in Hawai'i is doing: fine regional Italian cuisine that is so ingredient-driven and seasonal that portions of the menu change daily, and he won't serve a tomato unless it's summer.

Sakai's is slow food created only by constant care: care in selecting the base ingredients; care in concentrating and layering flavors by various means including smoking, curing and aging (specialties of his); care in preparing everything to order so that it arrives at its peak.

Take the house-cured duck prosciutto with blood orange, MA'O farm frisee, Banyuls vinegar and Fontina fondue ($13.50). A salad is an excellent test of a restaurant: There's very little to hide behind, and it illustrates the culinary principal that simple is difficult.

In this salad, just a few morsels of cured duck were sufficient, striking up a symphony with the sweetness of the fruit, the crispness of the frisee, the creaminess of the cheese and the complex earthiness of the aged wine vinegar. When you go out singing the salad, you know it's a great restaurant.

But soon we were also singing the praises of the cold-smoked hamachi ($16) with avocado, Meyer lemon, French radishes and a drizzle of silky olive oil. The smoking was carried out with a deft hand that didn't overpower the fish but raised it to a more interesting level. An exceptional dish.

Then there was the tagliatelle alla carbonara with house cured pancetta stesa (a rich form of ham that is cured and air-dried), black pepper and Parmigiano Reggiano ($17). How many gloppy, over-cheesed, under-flavored, soggy-pasta'd carbonaras has the world endured? Here was one where the pasta was tender and toothsome, and the complementary ingredients lay as lightly on the noodle ribbons as a gauzy scarf on a woman's shoulders.

Even my husband's soup of the evening ($10) — a cream of sunchoke — got raves with its drizzle of truffle oil and a certain light meatiness. The use of sunchokes and other root and winter vegetables rarely seen on Island menus illustrates Sakai's belief that just because a product is available year-round doesn't mean it's at its best.

The proof of a great meal is in the sighing and smiling: During two dinner visits with friends, there were repeated instances of those involuntary moans and murmurs and those sudden pleasurable grins that people give when they're surprised and delighted by a first bite.

Sakai has had a bit of an uphill battle; it's difficult for some customers to appreciate the ideas that inform this menu. From Suzette Gresham at Aquarello, Sakai learned to understand Italian food within its cultural context, to embrace its regionality, seasonality and essential simplicity. The approach spoke to his soul because he'd begun to tire of overfussy food.

"In cooking," he said in a post-dining interview, "people sometimes lose sight of the dish itself. My rule of thumb is I try to keep three or four ingredients on a plate and no more. And after we come up with a dish, we try to analyze its essence and pull away as much as possible. If you take that approach, you have a dish that is very complete, but nothing is overshadowing the essence. It's a simpler, purer, cleaner approach."

In this, the kitchen never stumbled. Everything we ate made sense and worked as a whole, which is sadly rare.

Even more rare is to be able to praise the waiters' knowledge not only of their own menus but of the local restaurant scene, of wine (at least within my limited knowledge of that topic) and of the principles of good service. Neither Brett nor John, the servers who assisted us on different nights, hovered, interrupted, disappeared or said anything that made me want to roll my eyes.

You'll experience some things at Diamond Head Grill you've not tasted before. Walu (aka escolar, oil fish; $30) is a tricky fish because of its oil content, but pan-roasting proved an excellent treatment paired with caramelized globe artichokes and an herbed lemon broth. Grilling prawns ($29.50) is another potentially fraught operation because shrimp overcook so readily, but the Australian saltwater blue prawns were still moist, and the accompanying cannelini beans with guanciale (dry-aged and seasoned pork jowls) added richness. My favorite of the entrees was the Snake River Farms Kurobuta pork rib chop with Umbrian farro, a grain rather like barley ($33), which epitomized the way that this menu marries sophistication and rusticity.

Put yourself in the hands of the menu when it comes to wines. All the recommended pairings were very pleasing, if painfully pricey ($8 to $22 a glass, with most at $10 to $12). A nice, if costly, feature is that, because it's truffle season, you can order a few shavings of truffles ($1 per gram for Oregon white, $5 per gram for Perigord black) added to select dishes.

Pastry chef Charlene Leong is as adventuresome as Sakai, with a menu including olive oil gelato with extra-virgin olive oil, sea salt and balsamic strawberries ($9) and (winning the prize for longest menu name) peanut butter mousse bombe with a peanut butter feuillantine crust, chocolate pepper truffle, anglaise and black pepper gelato ($10). Try the bombe: You'll never look at a Reese's peanut butter cup the same way again.

So why am I not giving the restaurant five forks?

In another life, Diamond Head Grill is also the Wonderlounge, a nightclub. So it is that while you're enjoying a gracious (and very expensive) meal, the staff is setting up for the text-message crowd, arranging tables of booze, tinkering with the sound system and so on — distracting and detracting from an otherwise charming culinary experience.

This kind of room bifurcation is going on all over town. I sympathize with the fact that restaurant owners have to make rooms pay, but fine dining and a club atmosphere don't mix. Some way of screening the restaurant from the club until dinner service is complete would solve this problem.

Reach Wanda A. Adams at wadams@honoluluadvertiser.com.