1. Make up devil's-food-cake mix as package label directs. Bake, in greased 10-inch tube pan, at 350°F. 45 minutes, or until cake tester, inserted in center, comes out clean; partially cool.
2. Meanwhile, combine corn syrup and rum, stirring until well blended. When cake has been out of the oven about 15 minutes, slowly pour half of rum syrup over top of it, in pan; let cool completely.
3. Remove cake from pan; turn upside-down on serving plate; pour rest of rum syrup over it. Let stand several hours.
4. Just before serving, whip cream; spoon on top of cake; sprinkle with grated chocolate.