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Peanut Butter Sheet Cake

This Peanut Butter Sheet Cake is for true peanut butter lovers. A layer of fluffy peanut butter cake topped with a layer of lusciously creamy and easy peanut butter frosting.

2 slices of peanut butter sheet cake sitting atop one another

Hi there, Marie here from Sugar Salt Magic and when I need an excuse to eat peanut butter by the spoonful, sans judgement, this peanut butter sheet cake is the answer. It is a wonderful combination of not too sweet but super soft and moist cake filled with an unmistakable peanut butter flavour.

And that frosting, sitting all swirly and soft on top, is more of that same PB flavour but in a creamy, melt in the mouth texture that just can’t be beat.

Close up of peanut butter frosting sprinkled with chocolate shavings

You’ve got to love a sheet cake. Perfect for family gatherings or dessert over a few days, they’re quick to make and just as delicious as a layer cake. This classic Chocolate Texas Sheet Cake is a family favourite as is my Almond Lemon Poke Cake too.

This peanut butter cake is made in a 9×13 pan so you can get 24 serves out of it but, to be fair, you’ll likely want to go back for a second piece, it’s that good.

A montage of photos showing how to make peanut butter sheet cake

How to make Peanut butter Sheet cake

All the usual suspects, except maybe the substitute of oil for butter which adds moisture to the whole cake, this is a simple mix and go affair.

  1. Beat together creamy peanut* butter, oil, sugar* and vanilla until it’s all mixed together well.
  2. Add eggs, 1 at a time and make sure they are really well beaten in before moving on.
  3. In a separate bowl whisk together* the flour, baking powder and salt then add 1 third to the wet mix and mix with a spatula until just combined.
  4. Alternate the milk and remaining dry ingredients, ½ of each at a time and stirring through with a spatula until just incorporated.
  5. At this point you have what looks like a big bowl of peanut butter, yum! So pour it into your baking tin and level it out then bake for roughly 20 minutes. 

Important cake notes:

  • You’ll get the best results from regular creamy peanut butter in this cake, as opposed to the natural PB types.
  • You’ll find 2 types of sugar in this cake – white and brown – and this combination is very important. All white sugar will leave your cake drier with a tighter crumb. All brown makes the cake far too dense but half of each gives it the perfect texture and flavour you need with slight caramel undertones.
  • ‘Whisking’ the dry ingredients separately – It takes just 30 seconds and I know it’s an extra bowl but doing this means your flour, salt and baking powder are not only evenly dispersed but the whisk helps to fluff the ingredients up which helps to add lightness to the cake.

2 images showing peanut butter frosting on a sheet cake

How to make easy Peanut Butter Frosting

The steps to making this luscious, incredibly creamy PB frosting could not be simpler.

  1. Beat together the peanut butter, butter and ¼ cup of the powdered sugar until smooth and creamy.
  2. Add the remaining powdered sugar ¼ cup at a time.
  3. Add the vanilla and salt, then beat for 2-3 minutes until it looks creamy and whipped.

Important frosting notes:

  • As with the cake, regular creamy peanut butter will give the best result.
  • Adding a little sugar right at the start, helps the butter and peanut butter emulsify together.
  • Adding the rest of the sugar ¼ cup at a time is just to stop it puffing up all over the kitchen and you.
  • Brands of sugar, peanut butter and, for that matter butter, do vary in their moisture contents so you can thin or thicken the frosting with more or less powdered sugar to get it just the way you like.

I could seriously eat this stuff straight off a spoon. The Peanut butter itself has a wonderful consistency where it can hold it’s own shape, so this buttercream only needs enough powdered sugar to hold the butter making this frosting not only super peanut buttery but not sickly sweet. Aka perfect for eating off a spoon.

slices of peanut butter sheet cake on a sheet of baking paper

This cake keeps well for 3-4 days in an airtight container in the fridge. Let it come to room temperature before eating.

Can you freeze peanut butter cake?

You can definitely freeze this peanut butter cake, frosting and all. Sliced or unsliced is fine too.

The very best way to freeze it is to place it into the freezer uncovered on the baking tray first, then;

  • Sliced – wrap the individual slices in plastic wrap before storing them in an airtight container for up to 2 months.
  • Unsliced / full cake – wrap the entire thing (cake pan included if you can spare it), in a layer of plastic wrap, followed by a layer of tin foil, then another 2 layers of plastic wrap. This will keep for up to 2 months.

Thaw the cake in the fridge overnight. Single slices are fine thawed at room temperature in about ½ an hour (depending on how warm or cool your home is).

a slice of peanut butter sheet cake on a white saucer

This peanut butter sheet cake with it’s dreamy peanut butter frosting is truly a dream cake for peanut butter lovers. It’s loaded with PB flavour and easy to make – bonus points that it can be frozen so you can fulfil your PB cake desire whenever you need.

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2 slices of peanut butter sheet cake sitting atop one another

Peanut Butter Sheet Cake

0 from 0 votes
Prep Time: 20 minutes
Cook Time: 20 minutes
Total Time: 40 minutes
Servings: 24 serves
This Peanut Butter Sheet Cake is for true peanut butter lovers. A layer of fluffy peanut butter cake topped with a layer of lusciously creamy and easy peanut butter frosting.

Ingredients

FOR THE PEANUT BUTTER CAKE

  • 2 cups (9 1/4 oz) all purpose flour
  • 2 teaspoons baking powder
  • 1/4 teaspoon salt
  • 1/2 cup brown sugar
  • 1/2 cup white granulated sugar
  • 3/4 cup creamy peanut butter
  • 1/2 cup vegetable oil
  • 2 teaspoons vanilla
  • 2 large eggs
  • 3/4 cup whole milk

FOR THE PEANUT BUTTER FROSTING

  • 3/4 cup (1 1/2 sticks) unsalted butter, softened
  • 3/4 cup creamy peanut butter
  • 1 1/2 cups powdered sugar, sifted
  • 1/2 teaspoon salt
  • 1 teaspoon vanilla
  • Chocolate shavings

Instructions

FOR THE PEANUT BUTTER CAKE

  • Preheat the oven to 350F. Grease and line a 9x13 baking tin with baking paper.
  • In a medium bowl, whisk together the flour, baking powder and salt.
  • In a large bowl, or the bowl of a stand mixer with paddle attachment, beat together both sugars, peanut butter, oil and vanilla until fully combined. Scrape down the sides.
  • Add the eggs, one at a time, beating well between each and scraping sides of bowl as necessary.
  • Add 1/3 of the flour mixture and fold through with spatula. Follow with half the milk and mix through gently, then repeat the process - flour, milk, flour.
  • Spread the batter into the prepared tin and bake for 18-20 minutes until a toothpick inserted, comes out with just a crumb or two but not wet batter.

FOR THE PEANUT BUTTER FROSTING

  • Beat together the butter, peanut butter and 1/4 cup of powdered sugar until smooth and lightened.
  • With the mixer on low, add the sugar quarter of a cup at a time and continue to beat until fully combined.
  • Add the vanilla and salt, then beat on high for 2 minutes until fluffy and creamy.
  • Spread over the cooled cake then scatter with chocolate shavings.

Notes

  1. It's always best to weigh flour using a kitchen scale to give the best results. If you use cups, make sure to fluff up the flour first, then spoon and level.
Nutrition Facts
Peanut Butter Sheet Cake
Amount Per Serving (63 g)
Calories 270
* Percent Daily Values are based on a 2000 calorie diet.

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About the authors

carrian feik cheney oh sweet basil

Cade and Carrian have three children and love to spend time together whether it’s vacationing or snuggled up on the couch for a good movie.

And this family especially loves to eat.

They love everything from the keep you fit and healthy to the get out your sweat pants indulgent and everything in between.

But most of all, they love the memories made, shared and treasured and it’s all thanks to a meal shared together with loved ones.

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