WHAT’S a two-star restaurant doing in a one-iguana town?Serving up the haute-est cuisine ever to hit the Osa Peninsula,on the country’s southwestern coast. The town of PuertoJiménez will never be the same, now that residents and visitorshave gotten a taste of the great food at El Restaurante Jade Luna.Experienced restaurateur Barbara Burckhardt has pulledout all the stops to make her restaurant chic but casual, withthe focus on imaginative and memorable food. She has planteda gorgeous garden to provide idyllic views from her elegantlyarcaded, tiled-terrace dining room, and has hired localartists to paint flowers and birds on her walls. Most importantly,she has scoured the country for the best and freshestingredients: goat cheese from Cartago, east of the capital;fresh herbs that arrive by bus from the Ark Herb Farm inHeredia, north of San José; shrimp and fish just off the boatfrom Golfito, across the waters of Golfo Dulce; and fresh pork,beef and eggs from nearby farms.THE impressively varied and sophisticated dinner-onlymenu changes daily, according to whatever is freshest that day.But even before you have a chance to zero in on the menu, asmall dish of pâté appears, with warm rounds of homemadetoast. One taste of the chicken livers transformed into pepperysilkiness and you know you are in for a seriously good meal.Appetizers are intriguing enough that you could make ameal out of them. Delicate smoked trout comes with a cloud ofdilled natilla (sour cream) and an accent of pickled red onion($5.50). A roasted vegetable and goat cheese tart combinesflaky pastry and garlicky, peppery filling ($5.50). Dependingon the day’s catch, there could also be crisp, Caribbean-spicedconch fritters ($5.50) or a velvety mushroom and smoked oysterbisque ($4.25).THERE’S nothing ho-hum about the salads here.Burckhardt tosses mixed greens with green-apple and orangeslices, toasted pecans and fried goat cheese, and then drizzleson a raspberry vinaigrette ($5.50). The Greek salad is asauthentic as you can get, with imported olives, feta cheese, artichokehearts and roasted red peppers ($5.50).You may be tempted to fill up on bread warm from theoven, with real butter (not the blister packs of ersatz “low-cholesterol”mantequilla masquerading as the real thing throughoutCosta Rica). But resist, if you can. Not only are the entréesmouthwatering and creative, they’re also substantial. ButteryDauphinoise potatoes and sautéed mixed vegetables usuallyaccompany the main courses.Kitchen assistant Karen Vargas, whom Burckhardt is training,sometimes contributes a side dish that’s difficult, at first, toidentify. The mystery side turns out to be camote (sweet potato)mashed with cream and butter, topped with a coconut-pecancrumble, reminiscent of an American Thanksgiving casserole.DEPENDING on what the fishermen bring her,Burckhardt always has fresh fish, often blackened Cajun-style,with a side of pineapple salsa ($10.95). She serves the jumbo shrimp straight out of the gulf and straight up, grilled withlots of garlic ($15.25). There’s always a pasta special anda chicken-breast dish, often with a mustard and tarragonsauce, but Burckhardt uses whatever unexpected ingredientscome her way.The weekend my friends and I sampled Jade Luna,Burckhardt’s U.S. houseguest had brought her dried sweetcherries, so the chicken of the day was blanketed in a cherrybalsamic sauce ($10.95).IN the three years before she opened the restaurant,Burckhardt established her reputation in the area by whippingup smooth ice creams and refreshing fruit sorbets, sothe dessert menu leans heavily toward the rich, creamystuff. You can order scoops of house ice cream, choosingfrom vanilla bean, chocolate, coffee, rum raisin and strawberry,or more exotic ginger or green tea ($3.25). Sorbetsusually include mango, pineapple or mora (blackberry).But Burckhardt’s frosty pièce de résistance is a pecan pralineice cream pie with caramel and chocolate on an old fashionedgraham-cracker crust ($3.25).As with the kitchen staff, Burckhardt is training localsto serve, and the table service is certainly attentive andfriendly, if not yet completely polished. The wine list alsois not yet up to the quality of the food, although the twoSpanish and two French wines (red and white, $16-23) area cut above the lower-echelon Chilean wines on offer inmost out-of-the-way restaurants.But as you sit in the elegant terrace restaurant, bathedin candlelight, surrounded by a sophisticated soundtrack,you can forgive these small failings, especially when youremember you are on the fringes of civilization. Here youare, just a stone’s throw from the wilds of the OsaPeninsula, enjoying a world-class meal that would cost afortune in the concrete jungle of Manhattan.Jade Luna (735-5739) is open for dinner, 5-9 p.m.,Monday to Saturday. You’ll find it just southeast of thePuerto Jiménez airstrip, across from the old cemetery, onthe road to Playa Platanares.