At L'Ecole, the student-run restaurant at the French Culinary Institute in SoHo, they're mixing drinks with a light saber. Well, not really. But something close. Dave Arnold -- whose official title at the institute is director of culinary technology, though mad scientist in residence might be more accurate -- was behind the snug, window-front bar, playing with his newest toy. It sits at the corner of the zinc bar: a steel box with a digital temperature gauge, topped with a kind of metal holster. Resting in the holster is a 16-inch nickel-alloy rod -- the light saber -- that's wired, through its handle, to the box.