THE DINING DOWN UNDER IS MOVING UP IN CLASS

We can probably thank Paul Hogan and koalas for the recent surge of interest in Australian food. But as more and more Aussie restaurants open in America featuring meat pies and creamy desserts named after ballerinas, you can’t help wondering what they are really eating over there.

The answer is not quite what you’d expect. Dining Down Under has come a long way from cold spaghetti and bean sandwiches. Although these still exist, the influx of “new Australians” from Europe and Asia has given birth to thousands of exciting new restaurants.

All prices are given in Australian dollars; the current rate of exchange is $1 U.S. to 73 cents Australian. Prices are not excessive and a 10% tip is considered adequate. A minor annoyance is that there’s a surcharge, usually around $3 per person, on weekends and holidays; perhaps that’s the time to get yourself invited to somebody’s “barbie.”

FISH

Seafood in Australia is absolutely wonderful, and although it is always slightly more expensive when it is grilled, it’s worth paying the price. One of the best places to eat fish is on the casual beachside terrace at Doyle’s on the Beach, which boasts its own family fleet.

While admiring the view of Watson’s Bay and the city skyline beyond, savor sand whiting, barramundi, mulloway, marong, jewfish and other wonderfully delicate and fresh-tasting species we simply do not get at home. On a warm day, I suggest cold lobster salad, actually a giant New South Wales crayfish, fresh eight months out of the year, with a Tabasco-spiced Louis dressing and potato salad. If it’s chilly, try the hot seafood chowder in a snapper stock broth. Big eaters will be happy to hear that they can have seconds (and more) of any fried fish at no extra charge.

Be sure to make a reservation or you’ll have to queue up with the rest of the blokes. Doyle’s is also accessible by water taxi from downtown’s Circular Quai.

Doyle’s on the Beach, 11 Marine Parade, Watson’s Bay, 337-2007. Open daily from noon to midnight, Sundays until 10 p.m. Cocktails, beer and wine. BC (Australian Bancard), MC, V. Dinner for two, food only, about $60.

Another fine place for fish is a historic, 180-year-old former warehouse with a view of the Opera House and Harbor Bridge. The Waterfront is a casual place that is considered reasonable even by the natives. Appetizers (called entrees in Australia) include an assortment of cold seafood and lobster-like Moreton Bay bugs, fresh ocean prawns, blue swimmer crabs (which resemble tiny Dungeness with skinny legs but great bodies) and those justly famous Sydney oysters.

Main courses come with chips and a family-style salad of sprouts, tomato wedges and onions. Greens include mignonette and cos, known to us as bronze lettuce and romaine. You’ll love the John Dory, which is Australia’s finest, simply grilled. On the other hand, they do have whole baby schnapper, bream, deep-water dory, gemfish and ocean perch. Tasmanian lobster is $25. Service is young and friendly, a la Marina del Rey, without the introductions.

Waterfront, 27 Circular Quai West, The Rocks, 241-2951. Lunch and dinner daily. Cocktails, wine and beer. Complimentary valet parking with courtesy bus. Dinner for two, food only, $55.

ELEGANCE

Prunier’s, Sydney’s oldest restaurant, is in an exquisite garden villa setting with French doors overlooking a tiled patio and park. Discreetly hidden behind a small park, this is where the Establishment wines, dines and shines.

The food includes everything from baked lamb brains to hot passion fruit souffle, and the artistic presentations are certain to charge the adrenaline of the most jaded foodie. Starters include sea trout carpaccio, pumpkin-yogurt soup or the luscious Queensland crab, similar to Florida stone crab, served with avocado mousse and lime vinaigrette. The French and Greek chefs collaborate on such delectables as roast Aylesbury duckling, Tasmanian sea trout fillets (baby salmon) in Portuguese sauce or a sweet-fleshed schnapper tail studded with oysters. Best of all is the lean, rosy, baked fresh lamb filet from New South Wales.

Prunier’s Chiswick Gardens, 65 Ocean St., Woollahra, 321-974. Weekday lunch; dinner nightly from 6:30 p.m. Cocktails, beer and wine. Banquet room. Street parking. Closed Sunday. Dinner for two, food only, $80.

A NIGHT AT THE OPERA

No visit to Sydney is complete without a visit to the Opera House, whose “mating butterflies” architecture enjoys world fame. If you want to combine it with a meal at its Bennelong restaurant, be sure to reserve your table as soon as you obtain your tickets, as it is frequently “booked out.”

The restaurant is contemporary, with a beautiful view of Sydney’s skyline and harbor. The prix-fixe meal is multichoice, the a la carte dishes not unimaginative. For openers, there’s prosciutto gateau with watercress sauce, ragout of Jervis Bay mussels or a salad of marinated scallops and squid. As a main course, you can have grilled duck with turnips, sweetbreads with mushrooms or basil and garlic tortellini.

Desserts alone are worth a visit. I tasted something called gooseberry fool, a mousse-like creation in a goblet, and an almond chocolate gateau, a masterpiece in the finest Viennese tradition, mit Schlag . Service is swift; they know the meaning of curtain time.

The Bennelong, Sydney Opera House, Bennelong Point, Circular Quai, 250-7578. Lunch, dinner and late supper daily. Cocktails, beer and wine. All credit cards. Dinner for two, food only, $40-$60.

SWEETS

The Gelato Bar, a European cafe located on Sydney’s No. 1 beach, has hefty portions of Old World staples like goulash, schnitzel, Hungarian roastbraten and boiled beef with horseradish. But it’s the gelato that is on everyone’s lips, and the pastries are the best in town. Favorites include apple and cheese strudel, walnut-plum cake, vanilla cream slices, chestnut puree with whipped cream.

Gelato Bar, 140 Campbell Parade, Bondi Beach, 304-033. Lunch and dinner daily until midnight. BYOB; corkage, 50 cents per person. BC, MC, Visa. No reservations. Dinner for two, food only, $25.

ROOM WITH A VIEW

The Summit, world’s largest--and Australia’s highest--revolving restaurant, is on the 47th floor of a building dedicated in 1968 by Sir Edmund Hillary, conqueror of Mt. Everest (he took the elevator here). In the middle of downtown, this is a special occasion spot for Sydneysiders.

The buffet’s the thing here; it is truly lavish. You’ll eat royally after drinking in more of the incredible 50-mile view as you walk about, especially if the weather is clear. (The forecasts down under are uncannily accurate.) Help yourself to fresh local fish (don’t overlook the smoked mussels), various hot and cold meats, salads, sausages, cheese, fruit dessert and coffee.

Summit, Australia Square, George and Pitt streets, entrance off Bond. 279-7777. Lunch, dinner and late supper Monday through Saturday. Buffet lunch Sunday. Dancing to live music until midnight. Cocktails, wine and beer. All major credit cards. Buffet Monday-Friday: $22 for lunch, $32.50 for dinner. Sunday lunch $27.50. Public holidays $29.50.

HONORABLE MENTION

If the craving for Chinese food comes over you, Bambusia Beachfront Restaurant has some fine dishes, several with Indonesian influences, and all attractively presented, beef fillet satay, scallops Bambusia, sizzling prawns in plum sauce and mixed vegetables in a log. 138 Curlewis St., Bondi, 300-0487. . . . On a shopping spree in Double Bay? It’s Sydney’s Beverly Hills, dubbed “Double Pay” by the native wags. There’s George’s , where you can dine in Byzantine splendor on Continental favorites, 419 New South Head Road, third floor, 327-1961. . . . Homesick for California? The trendiest spot of the moment is Chez Oz , where a Puck-ish menu with a Sydney slant features smoked salmon with American Golden Caviar, barbecued leg of lamb with green beans, charcoal broiled veal with eggplant, in an intimate, tres chic room or on the outdoor patio. 23 Craigend St., Darlinghurst, 332-4866. You’ll be happy to hear that designer pizza and fajitas have not yet come to Australia.