Heat the cream and corn syrup in a saucepan or in the microwave, until the mixture begins to steam., Pour over the chopped chocolate in a bowl. Let sit for 5 minutes. Stir — at first slowly, then more vigorously — until the chocolate is completely melted. If necessary, reheat very briefly to soften any remaining hard bits of chocolate. Flavor to taste (see "tips," below), if desired., Use ganache while the chocolate is still warm, but has begun to thicken. Reheat if it thickens too much as you work., Leftover ganache may be stored in the refrigerator, covered, for at least a week. Reheat at a low temperature to make it spreadable or pourable.