01 -
Preheat oven to 350°F. Spray a 9x13-inch baking pan with nonstick cooking spray. In a large bowl, combine chocolate fudge cake mix, instant chocolate pudding, eggs, oil, and Dr Pepper soda. Mix on medium speed with an electric mixer for about 2 minutes until smooth.
02 -
Pour batter into prepared baking pan. Bake according to package directions, usually about 40 minutes. A toothpick inserted in the center should come out clean. Allow cake to cool slightly before frosting.
03 -
In a medium saucepan, melt butter over medium-low heat. Stir in cocoa powder and 4 tablespoons heavy cream. Remove from heat and whisk in powdered sugar until smooth, adding additional cream to reach desired consistency. Stir in vanilla extract.
04 -
Pour frosting evenly over warm cake and spread to cover. Sprinkle chopped nuts over the top if desired. Let frosting set as cake cools before serving.