Black and White Sheet Cake

Name: Black and White Sheet Cake
Prep time: 4 h 50 min
Cook time: 20 min
Total time: 5 h 20 min
Cuisine: American
Ingredients: 3 oz semi sweet or dark chocolate, chopped; 1 1/4 cup all purpose flour; 1/2 cup cocoa powder; 2 tsp baking powder; 1/2 tsp salt; 1/2 tsp espresso powder; 1/4 cup unsalted butter, room temperature; 1 cup granulated sugar; 1/3 cup vegetable or canola oil; 2 large eggs, room temperature; 1/2 cup sour cream, room temperature; 1/2 tsp vanilla extract; 1/2 cup whole milk, room temperature; 1 1/2 cups all purpose flour; 2 tsp baking powder; 1/2 tsp salt; 1/4 cup unsalted butter, room temperature; 1 cup granulated sugar; 1/3 cup vegetable or canola oil; 2 large eggs, room temperature; 1/2 cup sour cream, room temperature; 1 1/2 tsp vanilla extract; 1/2 cup whole milk, room temperature; 1/2 cup unsalted butter, room temperature; 2 cups powdered sugar, sifted; 1/2 tsp salt; 2 tsp vanilla extract; 2 TB heavy cream; 1/2 cup unsalted butter, room temperature; 2 cups powdered sugar, sifted

posted by Megan on Jun 8, 2023 0 comments »

Jump To Recipe

I’ve been dreaming of an iteration of this black and white sheet cake since I read my American Girl magazine back in the spring of 2000. It was their 10th birthday and they released a special issue featuring a reader-submitted recipe for a “people pleaser” 9 x 13 cake. So Jennifer L. of Virginia, this one’s for you!! Thanks for the inspiration 🙂

Jennifer’s original recipe called for boxed mix and canned frosting, which is a great starting point. But I’m always looking for a challenge, and converting this into a homemade sheet cake definitely ticked that box.

After some tweaking of both my favorite chocolate and vanilla cake recipes, I’m so happy with the results!! This black and white sheet cake is moist, tender and absolutely delicious. It feeds a nice sized crowd and has the perfect cake/frosting ratio. To quote AG Magazine…

“You simply can’t go wrong with this clever cake idea.”

stack of chocolate and vanilla cake slices, alternating in a pattern between the chocolate and vanilla. There is a silver sparkler on top and a jar of sprinkles in the background to the left.

The prep for this black and white sheet cake is a little more involved than just making a single batter, because we’re making two flavors. Don’t let that scare you, though! By doing a few things before beginning and following my tried and true process, you can streamline this and it won’t be as tedious as you think.

Be sure to use a half sheet pan and not a “cookie sheet” for this recipe. A sheet pan has higher sides and can easily accommodate all the batter.

Mise en Place

This practice belongs in every kitchen, especially when baking. All it means is to have all of your ingredients measured and ready to add as the batter comes together. That way, you aren’t scrambling to measure things as you need them and risking making mistakes.

Thankfully, both the chocolate and vanilla batter comes together the exact same way, with the exact same ingredients up until you add the flour mixture. I’ve included my exact workflow from ingredient prep to the oven. You’ve got this!

slice of chocolate cake with chocolate frosting and rainbow sprinkles, sitting in a purple sheet pan.

Prep & Bake Workflow

Preheat the oven.
Butter the sides of the sheet pan and line the bottom with parchment paper. It also helps to swipe a little butter on the bottom of the pan before adding the parchment. This helps it to stay in place better. I also like to draw a line with a non toxic marker (washable ones work great!) down the center of the parchment to help guide me when adding the batters to each side.
Melt the chocolate for the chocolate batter and set it aside to cool. It’s important that the melted chocolate has had time to cool before you add it to the batter. Melt it before you prep any of the other ingredients so that it has plenty of time.
Sift each batter’s dry ingredients together. The flour and baking powder measurements are a bit different for each flavor, so pay attention! The chocolate batter has cocoa powder and espresso powder, too. After sifting everything together, give each bowl a whisk and set them aside.
Set aside the wet ingredients. For both flavors, you have the same amount of eggs, oil, sour cream and milk, so portioning them out should be easier. Add the vanilla extract to each flavor’s measurement of sour cream, since those two ingredients are added to the batter at the same time. There is slightly more vanilla in the vanilla cake batter.
Grab two large mixing bowls and add the butter and sugar measurements to each one. Again, the butter and sugar are the same for each flavor.
Beat the butter and sugar for the first flavor for 1-2 minutes. You don’t have to decide which bowl is which flavor at this point. For this step, use a hand mixer to beat on medium low until the butter has mostly coated the sugar and disappeared (first minute). Then, increase the speed and beat for another 30 seconds – 1 minute until just a bit fluffier. You won’t get a paste, it’s going to look like wet sand. Repeat for the other bowl.
Add the oil to the first bowl and beat on medium high speed for another minute. Repeat for the other bowl.
Each flavor gets 2 eggs. Work with one bowl at a time, and only move on to the next bowl when both eggs are added to the first bowl. So add one egg to the bowl of your choice, beat it in. Add the second egg to that same bowl and beat it in. Move on and repeat for the other bowl.
Beat in the sour cream and vanilla extract measurements. Repeat for the other bowl. This is where you need to decide which bowl is vanilla and which bowl is chocolate. The bowl with more vanilla extract will be the vanilla cake batter. I use either a sticky note or a little painter’s tape to keep them straight.
Alternate adding the dry ingredients with the milk. Just like with the eggs, finish the first bowl of batter completely before moving on to do the second. I recommend finishing the vanilla batter first, and then you won’t need to clean off the beaters before diving right in to finish the chocolate. Add half of the dry ingredients and mix them in on low speed. Stream in the milk and blend it in completely, then add the remaining dry ingredients on LOW speed. Add the melted chocolate to the chocolate batter with the second half of the dry ingredients (cocoa). Mix until there’s a few streaks of dry ingredients left, and then fold each batter a few times by hand to finish.
Add the chocolate batter to one short side of the prepared baking sheet and the vanilla to the other. These batters are NOT overly runny, they are thicker and flow a bit like lava. This makes them a lot easier to manage. You should be able to empty each bowl on each side and have them stay mostly put.
Smooth each flavor out carefully to meet in the center of the sheet pan. Again, these batters are very easy to work with. Gently work each flavor from the opposite edges to the center line you drew on the parchment. If the line isn’t perfectly straight or centered, don’t worry! Mine wasn’t perfect even after 5 tests 🙂
Bake for 10-11 minutes and then rotate the pan. This can get a bit tricky, as the sheet pan is larger and the batter will still be quite jiggly at this point. Go slowly and don’t worry. I include this step because my oven has a hot spot on the left side, but if your oven does a good job of heating evenly, feel free to skip this step!
Bake for another 10-11 minutes. You might notice that the chocolate rises a bit more than the vanilla. This is normal and okay! The cocoa powder is responsible for that. As the cake cools, it will even out nearly perfectly.
Let the cake cool completely before frosting it.

black and white sheet cake in a purple pan, that hasn't been sliced yet.

Make the frosting

The easiest part of this black and white sheet cake aside from actually eating it 🙂 The chocolate frosting is slightly more work than the vanilla, but worth it. Wait until the cake has cooled completely before starting the frosting. To save on dishes, make the vanilla first, and then the chocolate, scraping the bowl in between flavors.

The vanilla is a small batch of simple American buttercream, made a with powdered sugar, vanilla, heavy cream and a little salt. I recommend using a hand mixer to make both flavors of frosting, since a stand mixer might have trouble mixing such a small batch well enough.

After making the vanilla, scrape out the bowl and beaters really well and then continue to make the chocolate frosting. Save yourself some dishes!

To make the chocolate frosting, you need all of the ingredients you did for the vanilla, just with some cocoa powder. Use a little more heavy cream to balance out the extra dryness from the cocoa, and be sure not to over beat either flavor. Too much mixing will create unnecessary air bubbles in the frosting.

Finishing the cake

Do you remember in grade school when you folded papers in half either like a “hot dog” or a “hamburger?” We baked the cake batter with the flavors splitting the pan in half like a “hamburger” or two wider sides. Now, we’re using both batches of frosting to split the cake on the long sides like a “hot dog” and create 4 different cake and frosting combinations.

When it’s all over, you’ll have the perfect sheet cake for serving larger crowds and picky eaters!