Preheat oven to 375 F degrees. Line a 9x13 inch pan with parchment paper.
Mix all the cake ingredients together on medium speed for 2 minutes. If you don't have Betty Crocker's super moist chocolate cake mix, make sure you follow the instructions on the back of the box.
Bake the cake for 30 to 35 minutes or until done. If you stick a toothpick in the center of the cake it should come out clean.
While the cake is baking, bring butter, cocoa, and cream to a boil in a small saucepan, stirring occasionally. Remove from heat, and stir in vanilla and confectioners’ sugar. Use while still warm. Remove cake from pan and remove the parchment paper from the cake. Place the cake back in the pan and pour warm chocolate icing over the cake. Let cool completely.