About as appealing as the milk and raw eggs cinema prizefighter Rocky Balboa ingests before each workout -- that's flan to many people. Slimy, rubbery, rich to the point of nausea. But flan is a dessert, like Shakespeare said about Cleopatra, of infinite variety. The classic milk-and-egg concoction doused with caramel may boast coffee, chocolate, mango, and even coconut flavors. Cream cheese can also form its base. A mighty fine flan of the last type is served at Joe's, venerable home to famed crab claws and celebrated key lime pie. Velvety, dense, voluptuous. The confection's high calories come at a rather high price -- nearly four bucks a slice. Perhaps that's a good thing. Eat it too often and you're liable to become a heavyweight of a different kind.