This Peanut Butter Sheet Cake is the stuff of peanut butter lovers’ dreams! Satisfy your PB and dessert cravings in one fell swoop with this moist and tender cake topped with heavenly peanut butter marshmallow icing.
Whenever I’m craving peanut butter (which is often, let’s be honest), this heavenly peanut butter sheet cake is my go-to. It checks all the boxes needed to satisfy the craving: peanut-y, creamy, just sweet enough, and perfectly soft and moist! This cake has peanut butter flavor without being overwhelming, dry or crumbly like some peanut butter desserts can be. Along with an incredibly tender texture that melts in your mouth it’s topped with creamy marshmallow peanut butter frosting. Everyone always raves about the frosting!
Anywhere it goes, this easy cake is a hit with peanut butter lovers, and just about everyone else. Bake it, freeze it, or enjoy it fresh for days! Snacking cakes don’t get more scrumptious than this.
What You’ll Need
Peanut Butter: You can use creamy peanut butter, or crunchy peanut butter for added texture! The choice is yours. You’ll need it for both the cake as well as the marshmallow peanut butter icing.
Flour: All-purpose
Buttermilk: This is the not-so-secret ingredient for cake that’s super moist and tender! Plus, the flavor adds a bit of tang. No buttermilk in the fridge? Check out my buttermilk substitute tutorial.
Butter: Unsalted or salted, cut into cubes, plus extra for the icing.
Eggs: Two large eggs bring the perfect texture to this sheet cake.
Vanilla: Pure vanilla extract is best for flavor, but imitation will also work in a pinch.
Vegetable Oil: Or another neutral cooking oil, like canola.
Evaporated Milk: Adds extra sweetness and smoothness to the icing.
Mini Marshmallows: The base for the delicious marshmallow and peanut butter icing!
Sugar
Baking Soda
Salt
How to Make Peanut Butter Sheet Cake
This cake is perfect for serving a crowd when it’s prepared in a sheet pan. For this reason, I love bringing it to potlucks and family gatherings! You can also make your peanut butter cake in a 9×13 pan (more details in my tips section below). For the time being, here’s an overview of how to make the perfect sheet cake:
Mix the Batter: Set aside the flour and dry ingredients in one bowl, and the buttermilk and wet ingredients in another. Next, you’ll prep the peanut mixture by bringing water and butter to a boil, and stirring in the peanut butter and oil. Add the peanut mixture to the flour mixture, followed by the buttermilk mixture, whisking as you go.
Bake the Cake: Pour the batter into a lined jelly-roll style pan. Bake the cake in the oven until the center is set and it passes the toothpick test (a toothpick inserted into the middle comes out clean).
Make the Icing: Bring the evaporated milk, sugar, salt and butter to a boil while continuously stirring. Once this is taken off the heat, melt in the peanut butter and marshmallows. While the cake is still warm, pour the icing over top. Use a spatula to spread it evenly across the cake, then leave it to cool. Once the cake is cooled completely, slice and serve!
Tips for Success
Can I Use a Smaller Pan?: If you’d prefer to make this peanut butter cake in a 9×13 inch pan, it will still be delicious! Just increase the baking time to 35-40 minutes to account for the extra thickness.
If the Peanut Butter Mixture Is Really Hot: Adding the peanut butter mixture to the flour first should be enough to cool it off before it’s combined with the eggs/wet ingredients. However, if you’re concerned that the mixture is still hot enough to start cooking the eggs, leave it for a few minutes to cool before going ahead with the recipe as directed.
Can I Use Natural Peanut Butter? I’d recommend sticking to Jiffy peanut butter for this sheet cake. Natural peanut butters have a tendency to separate, which can lead to mixed results.
Topping Ideas
I like to think of a sheet cake as my own personal canvas for all sorts of toppings! While this peanut butter cake is delicious all on its own, there are so many topping ideas you can choose from, too:
Mini peanut butter cups
Chocolate chips or white chocolate chips
Chopped nuts like peanuts, pecans, hazelnuts, or macadamia
Store peanut butter cake airtight at room temperature for up to 3 days. If you’d like to extend the shelf-life, keep it covered in the fridge for up to 4-5 days.
Can I Freeze This Sheet Cake?
Another wonderful aspect of a sheet cake is that you can make it ahead, and it freezes super well! Did I not promise this was the best cake for parties?
To freeze this peanut butter cake (and to avoid messing up the icing), once it’s cooled completely, pop the whole pan into the freezer to pre-freeze. When the sheet cake is frozen solid, wrap it in a double layer of plastic wrap plus an extra layer of foil. The cake can stay frozen for up to 3 months!
Thaw the cake overnight in the refrigerator before carefully unwrapping it. Voila! Your pre-made cake is ready to serve.
The stuff of peanut butter lovers’ dreams! You’ll love serving up a slice of this dreamy Peanut Butter Sheet Cake topped with peanut butter marshmallow icing. Perfect for gatherings and potlucks!
Scale
Ingredients:
Cake:
2 cups all purpose flour
2 cups granulated sugar
1 teaspoon baking soda
1/2 teaspoon kosher salt
2 large eggs
1 teaspoon vanilla extract
1/2 cup buttermilk
1 cup water
3/4 cup butter, cut into cubes
1/2 cup peanut butter (crunchy or creamy)
1/4 cup vegetable oil
Icing:
1/3 cup evaporated milk
2/3 cup granulated sugar
1/4 teaspoon kosher salt
2 tablespoons butter
1/3 cup peanut butter (creamy or crunchy)
1/2 cup mini marshmallows
1 teaspoon vanilla extract
Instructions
Cake:
Preheat your oven to 350°F. Line a 15x10x1 (jelly roll-style) pan with parchment paper. Coat with nonstick spray and set aside.
In a large bowl whisk together the flour, sugar, baking soda, and salt. Set aside.
In a small bowl whisk together the eggs, vanilla, and buttermilk. Set aside.
Place water and butter in a small saucepan over medium heat. Bring to a boil and remove from the heat. Stir in the peanut butter and oil, mixing until combined. Add this into the flour mixture and whisk until smooth. Then whisk in the buttermilk mixture until evenly blended.
Pour the batter into the prepared pan and bake for 20 – 25 minutes until the center is set and a toothpick inserted comes out clean.
Icing:
Stir together the evaporated milk, granulated sugar, salt, and butter in a medium sauce. Bring to a boil over medium heat, and boil for 2 minutes stirring constantly. Remove from the heat and stir in the peanut butter, marshmallows, and vanilla until combined and the marshmallows are melted.
Pour the icing onto the warm cake, spreading out evenly using an offset spatula.
Allow the cake to cool completely before slicing and serving.
Notes:
Store airtight at room temperature for up to 3 days.
