It seems a no-brainer that high-profile chef-restaurateur Laurent Tourondel (until recently, the "LT" of BLT Steak, BLT Burger, BLT Market and BLT Fish in Manhattan) would score with a casual-chic new burger spot in downtown Sag Harbor.

I arrive at 11:55 a.m., while the breakfast crowd still lingers over bagels and omelets in the cafe area; the dining room opens promptly at noon. I bide my time on a metal glider swing admiring the handsome horseshoe-shaped bar.

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Lunch kicks off with a bowl of neatly fried Horman's dill pickles, from which burst hot piquant juices. A salad of local heirloom tomatoes and arugula gets a salty edge from crisp bacon.

A classic burger topped with Jack cheese is deliciously juicy. Is the pricier Snake River Farm American Kobe better? A bit richer, more velvety, but no more satisfying. I'm less taken with an organic turkey burger, which, while herbal, is a bit dry. A real surprise is how good the spiced tuna burger (actually a tuna steak) turns out.

Major letdown: Fries (sweet potato, waffle and skinny) are the previously frozen sort. This from a native-born Frenchman? Quel dommage.

The "gone bananas" shake (with fresh bananas and dulce de leche ice cream) succeeds in temporarily shaking my world. So, too, does a deeply fudgy brownie a la mode with bourbon sauce.

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LT Burger in the Harbor: 62 Main St., Sag Harbor, 631-899-4646,