Black and White Marble Sheet Cake with Chocolate Fudge Frosting

swirly cake

If you’re wondering where the Chocolate Fudge Frosting that is supposed to top this cake is, you’ve already seen it in a previous post (and can see it again below), but this shot of the unfrosted cake shows the chocolate and vanilla swirls closeup, in all of their glory.

Backing up, this is a large sheet cake that is perfect for birthdays and other celebrations. The large, flat surface is easy to decorate and the cake can certainly serve a lot of people. In addition to the logistical advantages, a swirled cake is the way to please those who like both chocolate and vanilla . It was moist, with a tight crumb, and had an excellent flavor from butter, sour cream, chocolate and vanilla – a flavor that is best achieved in a homemade cake.

The trick to a good marble cake is not to over-swirl the batter, because that can cause your cake to lose the distinction between dark and light into a medium brown. Swirl a knife through once, making a serpentine through the batter, to get an even marble. If this is too minimal for you, add the batter to the pan in alternating dollops, then swirl the knife through.

The frosting was just amazing. It had a smooth, rich texture and an intense chocolaty flavor. Thick, but not stiff, it ran easily over the top of the cake and set up by itself. Unlike ganache, which could be described in the same way, the creamy chocolate fudge was not heavy. I definitely felt like a kid again when making it – not because I made chocolate fudge frosting as a kid, but because I was tempted to lick the bowl.

Black and White Marble Sheet Cake
1/4 cup sugar
1/4 cup cocoa powder
3 tbsp water, hot
1/2 tsp vanilla extract
2 1/2 cups all purpose flour
1 tsp baking soda
1/2 tsp baking powder
1 tsp salt
1 1/2 cups sugar
1/2 cup butter, softened
2 large eggs
1 tsp vanilla extract
1/2 cup sour cream (regular or low fat)
1 cup milk (whole or low fat)

Preheat oven to 350F and grease a 9×13-inch baking pan.
In a small bowl, combine 1/4 cup sugar, cocoa powder, hot water and 1/2 tsp vanilla extract. Whisk to combine and set aside.
In a medium bowl, whisk together flour, baking soda, baking powder and salt.
In a large bowl, cream together butter and 1 1/2 cups sugar until light. Beat in eggs one at a time, followed by the vanilla and sour cream. Working in two or three additions, alternate adding flour mixture and milk to butter mixture (ending with addition of flour), mixing until no streaks of flour remain.
Scoop out 1 cup of cake batter and stir into cocoa mixture.
Spread white batter into prepared pan. Top with chocolate batter and drag a knife through to create a swirling pattern (don’t over marble, though!).
Bake for 30-35 minutes, until a toothpick inserted into the center comes out clean and the cake springs back when lightly pressed.
Cool completely on a wire rack before frosting.

Chocolate Fudge Frosting
1 cup sugar
1/4 cup cocoa powder
1/4 cup butter, softened
1/2 cup milk (lowfat is fine)
2 tbsp light corn syrup
1/8 tsp salt
2-3 cups powdered sugar
1 tsp vanilla extract

Combine sugar and cocoa in a medium saucepan and whisk until cocoa is dissolved. Add butter, milk, corn syrup and salt, and cook over medium-high heat, stirring occasionally, until mixture comes to a boil (about 10 minutes). Continue boiling; stirring occasionally, for 6 minutes. Remove from heat and cool to room temperature (approx 1 hour). Beat in powdered sugar and vanilla and pour on cake. Frosting will spread easily and will set up itself after a few minutes.



  1. This looks decadent and delicious. Well done once again.

  2. For the frosting – is that unsweetened squares of chocolate or cocoa powder?

  3. I love how it’s “FudgeSearch” frosting on my browser. I actually did a double take. ;) “What’s FudgeSearch?”

  4. Stephanie – It’s cocoa powder. I don’t know what I was thinking when I typed just “unsweetened cocoa”! I’m fixing it now.

  5. Thanks! I have all the stuff to make this at home then. It sounds great!

  6. Made this last night. The white cake batter was the best cake batter I’ve ever tasted (just a finger-full of course!) It’s very pretty but I think I baked it too long; used a stoneware cake pan and the edges got a little stiff before the toothpick-in-the-middle came out clean. That might have dried it out a little, as well. As for the frosting, I don’t think I’ve ever tasted a chocolate frosting like that. Delicious. I was only able to incorporate 2 cups of powdered sugar into it, though as it would have been way too stiff with another cup. It did spread nicely and stiffen up nicely too. Any advice on what I might have done to make this happen? All in all, I liked it very much. I think I would use this recipe to make an all-vanilla cake in the future. Thanks for the great recipe.

  7. Sometimes I think that humidity and temperature can come into play when it comes to frosting making – especially if one is as fudge-like as this. I think I’ll modify the instructions to say 2-3 cups. As long as it reaches the proper consistency (and it sounds like yours did), you definitely didn’t do anything wrong.

  8. I don’t think I’ve ever attempted to bake a cake in a glass pan, but I’m glad that one worked because it sure looks pretty.

  9. Oh my, Nicole, this looks and sounds fantastic! I have everything to make this so it’s going on my “Make this soon” list. I might play with the recipe a little, too, to see if I can make a lower carb but still tasty version of it. Hmmm, I might even see about using this recipe in my Cook’s Choice Bowl Maker rather than a 9 x 13 inch pan. I could fill the bowl with a sweetened cream cheese mixture and that would be awesome, I think! Thanks for sharing such a great recipe!

  10. Made this cake yesterday and it is nearly all gone. Such great texture and flavour. Icing was relatively easy to make and well worth it. I expected it to be way sweet but was just right. Family loved it

  11. I would like to make this in cupcakes…do you think it would work?

  12. Tried this cake came out excellently, thanks for the recipe.

  13. Just wondering how many this would feed? Thanks.

  14. Can you make this cake in a bundt pan?

  15. the recipe looks great. I am planning for 60 people, should i double the recipe?

  16. I made this cake yesterday and it was just great. Thanks for the recipe.

  17. If I want to turn this into a layer cake, should I double the recipe, or will the one layer be tall enough to slice in half?

  18. I made this using a 13×9 pan – waited till the tooth pick came out clean, however the cake turned a little dry….also, the middle of the cake collapsed ..any suggestions? Thank you!

  19. I know this is an old post, but I did wonder: why all-purpose and not cake flour? Thinking of making this for my husband’s birthday. I can’t decide if I’ll use it as the base for an ice cream cake or make your yummy-sounding frosting instead with ice cream on the side!

  20. Tiffany – All purpose is just more common for most home bakers, so I use it in a lot of cake recipes. I do have several that use cake flour, too, though.

  21. Hi! Just a question.. can I use the same proportions with 9 inch round cake pans?

  22. Can I speed up the cooling process of the icing?

  23. Great frosting but how did you get it so smooth, I was not able to get it smooth at all.

  24. Amazing! Made this cake….and cupcakes several times! Perfection!

  25. I made the cake yesterday and it looks and smells fabulous. I started making the frosting this morning, waited for the mixture to come to room temperature and now it’s a solid thing on the bottom of the pan. What did I do wrong?

  26. Sara – It sounds like you might have either added too much confectioners’ sugar to your frosting or it is too cold in your kitchen. You can reheat the frosting to melt and and smooth it out to a spreadable consistency again – just don’t cool it as long this time, if it is too cold in your kitchen. If it is simply too thick, you can reheat it with a tablespoon or two of milk to thin it out.
    It should be quite thick as it cools, since you want it to set up on the cake, you just want to keep an eye on it so it sets up on your cake and not in your bowl.

    I hope that helps!

  27. Can I flip this cake out of the 9×13 pan and then frost it?

  28. Hi, does anyone know how many ppl does it feed?

  29. This cake turned out perfectly! The first time I made it , it was for my boyfriend’s birthday. He absolutely loved it. There wasn’t any left after a day. I plan on making it again for my cousin’s birthday. One thing that I did differently is I split the batter into 3 parts, mixed the chocolate and then added blue food coloring (my boyfriend’s favorite color). It turned out so cool looking!

  30. If I make this again, I would only cook for 28 mins or so. I took it out of the oven at exactly 32 minutes and it was overcooked along the edges and even the middle slices were dry. The frosting helped a bit, but it was still disappointing? It does look pretty though.

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