Puree raspberries in a food processor or blender. Press through a fine sieve; set aside.
In a saucepan, combine cocoa and cream. Add sugar, corn syrup, butter and raspberries; mix well. Bring to a boil over medium heat, stirring often. Boil for 8 minutes without stirring. Remove from the heat. Cool at least 15 minutes before serving.
Spoon over ice cream, pound cake or brownies. Refrigerate leftovers in a covered container for up to 1 month.