Peanut Butter Sheet Cake

Peanut Butter Sheet Cake AKA the perfect party cake. A soft and tender peanut butter cake made from scratch, topped with real chocolate frosting and plenty of mini M&M’s.

It’s party time 🥳

Whether you’re celebrating a birthday, a reunion, a promotion or just LIFE in general, this Peanut Butter Sheet Cake is the perfect dessert. A soft and moist peanut butter cake topped with fudgy real chocolate frosting and a scattering of M&M’s. 

It’s ridiculously good and easily feeds a crowd! 

I love using peanut butter in my bakes. Most recently, my Peanut Butter Chocolate Chip Cookie recipe made me swoon. But today, it’s all cake.

And I adore peanut butter cake. Not only does mixing in real peanut butter to the cake batter add plenty of flavour, but it makes the cake so soft and tender – and that makes me so happy because you know we have a zero tolerance for dry cake around here. 

Once you take fistfuls of that perfect Peanut Butter Sheet Cake, you have to finish it off with a bucketload of creamy chocolate buttercream. After all, we know that peanut butter and chocolate are a match made in heaven. 

And to make it as festive as possible, we’ve added a shower of mini M&M’s. You can decorate this Peanut Butter Sheet Cake however you wish of course, Reese’s pieces, chocolate chips or just a drizzle of peanut butter would be equally amazing. 

HOW TO MAKE PEANUT BUTTER SHEET CAKE FROM SCRATCH

• You will need an electric mixer or hand beater to make this Peanut Butter Sheet Cake. I also recommend using a quarter size sheet pan, roughly 9 x 13 inches. 
• Start with room temperature butter so you can beat together your butter and sugar easily. We use brown sugar for extra flavour and caster sugar for sweetness. If you don’t have caster sugar, use granulated sugar instead. 
• Next, comes the peanut butter. I recommend using a full fat peanut butter, like Bega, Jif or Skippy instead of a natural, healthy peanut butter which has a completely different texture. 
• Then comes, vanilla and eggs. Then the dry ingredients, plain flour and baking powder. The final ingredient is full fat milk. 
• Try not to over mix the cake batter and then bake your cake until a skewer inserted in the middle comes out clean. Perfection! 

TIPS FOR MAKING THE PERFECT CHOCOLATE BUTTERCREAM

• Temperature is everything. Make sure your butter is at room temperature. Your butter needs to be softened so it whips easily. But make sure it’s not too soft or melty by any means. It should be soft to the touch but still hold its shape.
• Sift your sugar. I’m guilty on more than one occasion of not sifting my sugar but if you want the perfect buttercream, you HAVE to sift the sugar. It’ll ensure it’s light, fluffy and mixes well with the butter – no lumps. 
• Use your milk sparingly. The perfect buttercream has just the right ratio of butter, sugar and milk. Too much milk will make your buttercream too wet and runny, while too little, will make it too thick. Add a tablespoon at a time to ensure the correct consistency. 
• Don’t overbeat the frosting. Once you add the chocolate, beat only until the frosting is melted and smooth – don’t over-mix. 

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Let’s Bake

Peanut Butter Sheet Cake

Yield Makes 20–24 slices 1x

5 Stars 4 Stars 3 Stars 2 Stars 1 Star

4.5 from 4 reviews

Prep: 40 minutesCook: 40 minutesTotal: 1 hour 20 minutes

An easy Peanut Butter Cake topped with chocolate frosting and M&M’s.

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Ingredients

Peanut butter cake

• 230 grams (1 cup / 2 sticks) unsalted butter, room temperature
• 180 grams (1 cup) brown sugar
• 100 grams (1/2 cup) caster sugar or granulated sugar
• 250 grams (1 cup) smooth peanut butter*
• 1 teaspoon vanilla extract
• 3 large eggs, room temperature
• 2 teaspoons baking powder
• 1/4 teaspoon salt 
• 315 grams (2 and 1/4 cups) plain flour or all purpose flour
• 240 ml (1 cup) full fat or whole milk

Chocolate frosting

• 115 grams (1/2 cup or 1 stick) unsalted butter, room temperature
• 150 grams (1 cup) good quality milk chocolate
• 375 grams (3 cups) icing sugar or powdered sugar, sifted
• 2–3 tablespoons full fat or whole milk, room temperature
• 1 tablespoon smooth peanut butter*
• 180 grams (1 cup) mini M&M’s

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Instructions

1. Peanut butter cake
   Preheat oven to 180 C (350 F) standard / 160 C (320 F) fan-forced. Grease and line a quarter sheet pan with baking or parchment paper.
2. Place butter and sugars in a large mixing bowl. Beat together with an electric mixer on medium speed until pale and creamy. Add peanut butter and vanilla and mix together until smooth and combined.
3. Next, add eggs, one at a time. Beat on a low speed to combine. Don’t worry if the mixture looks curdled – this is normal.
4. Add baking powder, salt and half of the flour, followed by all of the milk. Beat on a low speed to combine, then add the final half of flour. The cake batter should be thick and smooth.
5. Pour batter into prepare pan and bake for approximately 35-40 minutes or until cake is golden brown and a skewer inserted in the middle comes out clean. Leave in pan to cool completely.
6. Chocolate buttercream
   To make the frosting, place butter in a large mixing bowl and beat with an electric mixer on medium speed for a couple of minutes until pale and creamy. Meanwhile melt the chocolate in a microwave, stirring in between 20 second bursts, until just melted and set aside to cool a little.
7. Once the butter is very pale and creamy, add half the sugar and one tablespoon of milk and beat on low until the sugar is incorporated. Then, add the rest of the sugar and another tablespoon of milk, and again beat on slow until the sugar is incorporated before turning up to medium for another minute or so.
8. Next, add melted chocolate to the buttercream, ensuring the chocolate is still smooth and melted but is not warm. Add peanut butter. Beat until the chocolate and peanut butter is completely mixed through. If the frosting is a bit thick, add an extra tablespoon of milk.
9. Generously spread the chocolate frosting all over the cooled peanut butter cake. Scatter over mini M&M’s.

Notes

*Peanut butter: I recommend using a full fat processed peanut butter like Bega, Skippy and Jif for this cake, instead of a natural peanut butter.

Nutrition Information

Serving Size: 1 square Calories: 413 Sugar: 37.3 g Sodium: 100.5 mg Fat: 21.8 g Carbohydrates: 50.5 g Protein: 6 g Cholesterol: 57 mg

Nutrition information is a guide only.

Author: Jessica HolmesCategory: CakeCuisine: American

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Jessica Holmes

Hi, I’m Jess, the creator of Sweetest Menu and the author of Something Sweet. A self-taught baker and published recipe writer who can’t stop making easy and delicious baking recipes.