Enhanced Cake Mix Marble Cake

Ingredients

• 3 oz flour) cake flour all-purpose
• 0.3 cup canola oil or any vegetable oil
• 3 tablespoons natural cocoa powder unsweetened
• 4 large eggs 
• 0.5 cup granulated sugar 
• 3 cups powdered sugar 
• 0.3 teaspoon salt 
• 1 pinch salt if using butter unsalted
• 6 oz butter unsalted salted softened
• 1.5 oz bittersweet chocolate chopped
• 2 tablespoons cup heavy whipping cream sour
• 4 tablespoons butter unsalted melted (I used )
• 1.5 oz chocolate unsweetened chopped
• 3 tablespoons cocoa powder unsweetened
• 2 teaspoons vanilla 
• 15.3 oz betty crocker golden vanilla yellow with pudding added) good
• 1 cup water 
• 0.3 cup milk whole
• 3 tablespoons milk whole plus more if needed room temperature

Equipment

• bowl
• oven
• mixing bowl
• double boiler
• hand mixer
• microwave

Directions

1. Preheat oven to 350 degrees F. Spray two 9 inch round cake pans with sides that are at least 2 inches high, with flour-added baking spray.
2. Combine cake mix, sugar, salt, eggs, vanilla, oil, butter, milk and water in a large bowl (do not add flour yet). Beat with an electric mixer for two minutes, scraping sides of bowl well.
3. Add the flour and stir until mixed.In a small mixing bowl, mix together cocoa powder and sour cream. Stir in 1 cup of the vanilla batter.Divide vanilla batter evenly among pans. Drop globs of chocolate batter over the vanilla batter.
4. Bake for 30 minutes on center rack or until cakes test done.
5. Let cool in pans for 10 minutes, then carefully invert.
6. Let cool completely.To make the frosting, melt both chocolates in microwave or double boiler and set aside to cool for about 30 minutes. Beat the butter until creamy. Stir in the cocoa power, about a cup of the powdered sugar, and the slightly cooled (it can be a little warm) melted chocolate. Scrape sides of bowl and beat well.
7. Add remaining powdered sugar, then add milk, vanilla and salt, beating and scraping until you get the consistency you like.