Easy Marble Cake with Chocolate Frosting

So I recently came into an unwanted box of yellow cake mix. With our anniversary coming around I got to thinking how easy it would be to make a marble cake (which was served at our wedding) with a box of mix. Add to that my son conveniently flipping to a page featuring chocolate frosting in the KitchenAid book and Voila! an unending craving for chocolate frosted marble cake appeared. The concept was simple: prepare the mix, pour all but 1 or 2 cups into prepared pans, add hot chocolate mix to remainder and marble. Whip up a simple chocolate frosting recipe courtesy allrecipes.com. Frost. Done. Or maybe not?
After sticking the cake in the oven and creaming the butter for the frosting I discovered we had little more than half a cup of confectioner's sugar. No problem, right? I stuck some sugar and cornstarch in the food processor and processed the heck out of it. Whilst willfully ignoring the shiny glints of sugar crystals in the mix, I made up the frosting recipe. The crunchy and not fluffy frosting recipe. Not to be defeated I spend over an hour trying to cook the glop long enough that the sugar would melt (ha!). Several hours of frustration later my husband was boiling what was now inedible chocolate "candy" out of a pot, a Pyrex dish, and the mixer bowl. (Thank you!)
Still refusing to be conquered by such a simple task as whipping butter, cream, and sugar, I rushed off to the grocery store the next morning. I bought the biggest bag of confectioner's sugar they had and made a silent promise to never run out of it again! And after 5 minutes of easy labor later I had my chocolate frosted cake! And did I mention the frosting is free of hydrogenated oils, high fructose corn syrup, or animal lard (gross!) you're likely to find in the store bought variety? Hope you all are inspired by this recipe, though there is very little to it.

Ingredients:
Cake:
1 package of white or yellow cake mix, prepared
1 pkg or 4 tbsp hot cocoa mix

Frosting:
2 3/4 cup confectioners sugar
1/3 cup cocoa powder
6 tbsp butter, softened
1/3 cup cream or evap. milk
1 tsp vanilla

Directions:
Pour all but 1/3 of prepared cake batter into desired pan(s). Mix hot cocoa into remaining batter. Drop chocolate batter by the spoonful into the cake pans. To marble batter, pull a knife through the batter alternating forward and backward strokes starting at the left of the pan and moving towards the right. Turn pans 90 degrees and repeat. Bake according to directions provided with cake mix. Remove from oven and cool on a wire rack.

Cream butter with electric mixer. Combine sugar and cocoa. While mixing on low speed, alternately add sugar mixture and cream until combined. Add vanilla and beat on high until fluffy. Add additional cream or sugar if needed. When cakes are cooled apply frosting as desired. Enjoy!