In a small bowl let the raisins soak in the water. In a dry small heavy skillet heat the sugar over moderate heat, undisturbed, until it begins to melt, cook it, swirling the skillet occasionally, until it is a golden caramel, and remove the skillet from the heat. Add the raisins with the water, the butter, and the salt, stir in the rum, and cook the mixture over moderately low heat, stirring, until the caramel dissolved. Divide the ice cream between 2 dishes, halve the banana lengthwise and crosswise, and arrange 2 banana pieces in each dish. Spoon the butterscotch sauce over the ice cream and banana. Serves 2. Gourmet September 1993