Use this recipe when making our Devil's Food Cake wedding cake.
Place chocolate and cream in heavy saucepan. Cook over low heat, stirring constantly with a rubber spatula, until thickened, 20 to 25 minutes.
Increase heat to medium-low, and cook, stirring, 3 minutes more. Remove from heat; stir in corn syrup.
Transfer to a large metal bowl; refrigerate. Check every 15 to 20 minutes, stirring briefly each time, until cool enough to spread, about 2 hours.
For best results, do not double this recipe, but make it in batches.