This post may contain affiliate links. Please read my disclosure policy.

Fudgy, beyond rich chocolate sheet cake topped with the creamiest peanut butter frosting. Feeds a crowd!

chocolate sheet cake topped with peanut butter frosting, drizzle of melted peanut butter, and peanut butter cups in a baking pan

I saved a good one for today. I figured we can always use more peanut butter and chocolate in our lives. Especially if that chocolate is rich beyond belief, that peanut butter is in the form of frosting, and that cake is the size of Texas. And, of course, all those jazzy toppings.

Think of this as the single layer version of my towering chocolate peanut butter cake. Sheet cakes are quicker to bake and easier to decorate, which means you’ll be enjoying this cake even faster.

chocolate sheet cake topped with peanut butter frosting, drizzle of melted peanut butter, and peanut butter cups

I’m so excited because I’ve never shared a chocolate sheet cake recipe on my blog before.

I’ve made this chocolate sheet cake a handful of times for various parties and I remember making it for an office party back when I worked in an office. And the entire thing disappeared in about .04 seconds. People flocked to it like it was a pot of shimmering gold under a rainbow.

pouring chocolate mixture into flour mixture in a glass bowl

2 images of thick chocolate cake batter in a glass bowl and whisked eggs and sugars in a glass bowl

Some cake things you’ll need to know:

The first step we’ll do is melt down some butter with water and cocoa powder on the stovetop. This helps dissolve and hydrate the cocoa powder, which typically tends to dry cakes out. This also helps bring out the cocoa’s flavor. When mixed with a cup of butter, we have some seriously delicious chocolate liquid. Instead of water, you can use black coffee (like my favorite chocolate cake!). It’s completely incredible and truly deepens that chocolate flavor.

Then we’ll mix in all with dry ingredients. The usual suspects like flour, baking soda, and salt. Whisk eggs, sugars, and vanilla extract in another bowl. Combine all of these mentioned ingredients together, then whisk in some buttermilk.

chocolate cake batter in a glass bowl with a whisk

All of this chocolate magnificence goes into a half sheet pan.

Since it’s a thin cake, the bake time is quick, just like this funfetti sheet cake. Which means it won’t take long to cool, either. Which obviously means that you can cut into this chocolate cake and fall immensely in love sooner. But before all that, let’s frost it with the most unbelievable peanut butter frosting on the planet. It’s my go-to peanut butter frosting recipe, just made larger because this cake is enormous!

spreading peanut butter frosting onto chocolate sheet cake

↑ ↑ Best peanut butter frosting to ever grace this earth.

slice of chocolate sheet cake topped with peanut butter frosting, drizzle of melted peanut butter, and peanut butter cups on a white plate with a fork

One bite = super moist, fudgy, tender, and decadent with a party of texture on top in the form of: peanut butter cups, melted peanut butter, chocolate sprinkles, peanut butter chips, and more.

Print
clock clock iconcutlery cutlery iconflag flag iconfolder folder iconinstagram instagram iconpinterest pinterest iconfacebook facebook iconprint print iconsquares squares iconheart heart iconheart solid heart solid icon
chocolate sheet cake topped with peanut butter frosting, drizzle of melted peanut butter, and peanut butter cups

Chocolate Sheet Cake with Creamy Peanut Butter Frosting

  • Author: Sally
  • Prep Time: 30 minutes
  • Cook Time: 20 minutes
  • Total Time: 2 hours, 50 minutes
  • Yield: serves 2530 1x
  • Category: Cake
  • Method: Baking
  • Cuisine: American

Description

Fudgy, beyond rich chocolate sheet cake topped with the creamiest peanut butter frosting. Feeds a crowd! I encourage you to read the full recipe and the recipe notes before beginning so you’re completely prepared.


Ingredients

Scale
  • 1 cup (230g) unsalted butter
  • 1 cup (240ml) water
  • 1/2 cup (41g) unsweetened natural cocoa powder (not dutch-process)
  • 2 cups (250g) all-purpose flour (spoon & leveled)
  • 1 teaspoon baking soda
  • 1/4 teaspoon salt
  • 2 large eggs, at room temperature
  • 1 cup (200g) granulated sugar
  • 1/2 cup (100g) packed light brown sugar
  • 2 teaspoons pure vanilla extract
  • 1/2 cup (120ml) buttermilk, at room temperature*

Peanut Butter Frosting

  • 1 and 1/2 cups (405g) creamy peanut butter (do not use natural style)
  • 1/2 cup (115g) unsalted butter, softened to room temperature
  • 3 cups (360g) confectioners’ sugar
  • 1/2 cup (120ml) heavy cream, half-and-half, or whole milk*
  • 1 teaspoon pure vanilla extract
  • pinch salt
  • optional: 1/2 cup (135g) melted creamy peanut butter and 1 cup chopped peanut butter cups

Instructions

  1. Preheat oven to 350°F (177°C). Generously grease a 12×17 inch half sheet/jelly roll pan. Set aside.
  2. Heat the butter, water, and cocoa powder together in a large saucepan over medium heat. Whisk constantly until the butter has melted and everything is smooth and combined. Set aside. In a large bowl, whisk the flour, baking soda, and salt together. Pour the warm chocolate/butter mixture on top, then slowly whisk together until combined. It will be very thick.
  3. Whisk the eggs, granulated sugar, and brown sugar together in a medium bowl. The mixture will be thick. Whisk in the vanilla until combined, then pour into the chocolate batter and whisk until combined. Finally, whisk in the buttermilk. Pour the chocolate batter into the sheet pan.
  4. Bake for 15-20 minutes. (Mine takes exactly 17 minutes.) Use a toothpick to test for doneness: stick it into the cake. If the toothpick comes out clean, the cake is done. If not, continue baking. Remove cake from the oven and set the pan on a wire rack. Allow the cake to cool completely in the pan before frosting. The refrigerator helps speed things up, if you have room for the large pan!
  5. Make the frosting: Using a handheld or stand mixer fitted with a whisk attachment, beat softened butter and peanut butter together on medium-high speed for 2 minutes until completely smooth and creamy. Add the confectioners’ sugar, cream, vanilla extract, and salt. Beat on low speed for about 20 seconds, then gradually increase to high speed. Beat on high for 1 minute until combined and frosting is fluffy. Taste; add more salt if needed. To thicken, add more confectioners’ sugar and to thin, add more cream.
  6. Spread frosting all over cooled cake, and then top with toppings, if using. Slice and serve. Cover leftovers tightly and store in the refrigerator for up to 5 days. It’s so good cold!

Notes

  1. Make Ahead & Freezing Instructions: Cake can be made 1 day in advance, covered tightly at room temperature, and then frosted before serving. Frosting can also be made 1 day ahead of time– cover tightly and keep in the refrigerator. Bring frosting to room temperature before spreading. Frosted cake can be frozen up to 2 months; thaw overnight in the refrigerator and bring to room temperature before serving.
  2. Buttermilk: Buttermilk is required for this recipe. You can make your own DIY version of buttermilk if needed. Add 1 teaspoon of white vinegar or lemon juice to a liquid measuring cup. Then add enough whole milk to the same measuring cup until it reaches 1/2 cup. (In a pinch, lower fat or nondairy milks work for this soured milk, but the cake won’t taste as moist or rich.) Stir it around and let sit for 5 minutes. The homemade “buttermilk” will be somewhat curdled and ready to use in the recipe.
  3. Heavy Cream: Using heavy cream, half-and-half, or whole milk in the frosting produces the creamiest texture. (I use and highly recommend heavy cream.) If needed, you can use a lower fat or nondairy milk.
  4. Room Temperature Ingredients: Here is why the ingredients must be at room temperature. The butter is melted and warm, so it’s best the other ingredients are not cold.
  5. Toppings: We usually top this cake with melted peanut butter and chopped peanut butter cups. Use what you like best such as Reese’s Pieces or chocolate sprinkles. In some of the photos above, I also topped the cake with these Reese’s peanut butter sprinkle ice cream topping, a product I found near ice cream aisle.
  6. Sheet Pan: I own and love this 12×17 half sheet pan.
  7. Cake batter adapted from All Recipes.

Keywords: chocolate sheet cake, chocolate cake with peanut butter frosting

Add this to your weekend plans.

chocolate sheet cake topped with peanut butter frosting, drizzle of melted peanut butter, and peanut butter cups

Reader Questions and Reviews

  1. Frosting was incredible. I only used 2 C powdered sugar and it was still sweet and a great consistency. I rated this 4 because the cake was just okay—a bit on the dry side for my taste.

  2. Hi there, I am making a graduation sheet cake for my son. I have a 15 x 11, 2” pan. Would I be able to use this recipe. Appreciate your input.

    1. Hi Farah, you can, but there will be a little too much batter. You can fill your pan half way and then use the leftover batter for a few cupcakes. Enjoy!

      1. Hi Mey, you can use this frosting to pipe simple designs on the cake. You may want to refrigerate the frosting in the piping bag before using to help it keep its shape even better. Enjoy!

  3. I am hoping to make this cake today it looks amazing. I don’t have a sheet pan, can i use the tradition 9×13?

    1. Hi Charlotte, we’d recommend our triple chocolate cake instead (see recipe notes for 9×13 details) and then using this peanut butter frosting to top. Hope you enjoy it!

    2. actually i do have the right size pan, my question now is can I use pastry flour instead of AP?

      1. Hi Charlotte, we don’t recommend it. Cocoa powder is already a very fine ingredient so we don’t use cake or pastry flour as it will make the cake much too light and flimsy. Best to stick with all-purpose flour here.

  4. This cake is a peanut butter lovers dream cake. Very rich, flavorful, not too sweet and moist. If you love peanut butter you will love this cake.

  5. I’m wondering if I could add a strawberry sauce layer until the frosting layer. Would that work?

    1. Hi Meredith, We don’t see why not! Let us know how it turns out.

  6. Hello! Would the frosting get too messed up if I used natural style peanut butter? Processed peanut butter isn’t really an option because it costs way too much for whatever reason

    1. Hi Johana! The frosting may come out too runny or split from the extra oil of natural peanut butter.

  7. I would like to know if the cake with peanut butter frosting is made and frosted the previous day will it need to be refrigerated ? I’m doing a 3 tier 8 inch cake and won’t have the room to refrigerate. Thank you for your reply . Janet

    1. Hi Janet, after decorating anything with buttercream or cream cheese frosting, it’s fine for 1 day at room temperature. After that, we would refrigerate it. But, use your best judgment and whatever you are comfortable with- we’ve never had any problems leaving frosted desserts at room temperature for a day. Hope you love it!

  8. This is THE BEST chocolate cake I’ve ever had and the peanut butter frosting is amazing! My 8 year old grandson made this for my birthday with little help So moist and chocolatey!

  9. Another amazing recipe from Sally! I usually make her vanilla sheet cake to make number cakes and when a client asked for a chocolate cake I knew I could count on Sally! It’s delicious and extremely fluffy (which I love in chocolate cake) I used regular milk as I forgot to buy buttermilk and that worked perfectly as well.

    One tiny remark: I used a 9 x 13″ pan and the cake was still on the thin side so I think it would be extremely thin if you’re using the pan she mentions.

  10. I have used the frosting recipe many times and everyone that eats it cannot rave enough about had delicious it is.
    This is my go to frosting recipe for the rest of my LIFE.

  11. Second time trying this frosting and I just can’t get it to work. Followed the direction to a T both times and frosting is NOT creamy and spreadable like in the pictures. It’s more of a crumbly texture and doesn’t spread easily on the cake. Tastes amazing but looks like a huge mess. Wish I could figure out what the issue is because I’d love to have a good peanut butter frosting in my regular rotation.

Leave a Review!

Your email address will not be published.

Recipe rating

This site uses Akismet to reduce spam. Learn how your comment data is processed.