SMOKE AND MIRRORS: The fashion crowd knows what to do with a glass of Champagne, but what about a cube of smoked sea bass presented under a bulbous glass filled with smoke? Or a cubic potato resting on a perfect square of thinly sliced, er, rhubarb? The fantasy cuisine of French chef Thierry Marx stole the show Tuesday night as Moët & Chandon unveiled its 2000 vintage at a lavish event at the Paris Musée de l'Homme. Guests including Nathalie Rykiel, Bruno Frusoni and Didier Ludot dined on Marx's offbeat delicacies, washing them down with a medley of vintage wines and culminating with a dessert of sweet beets, topped with ginger ice cream. "Delicious! My best culinary experience in many years," declared French actor Stéphane Freiss.