Ultra-moist peanut butter sheet cake made with butter, peanut butter, milk, and sugar, topped with rich peanut butter fudge icing.
Okay, real talk — there are a lot of peanut butter cakes out there. I know it. You know it. Pinterest knows it.
But this Peanut Butter Sheet Cake? It’s different. It’s not just good — it’s the cake that made me believe in peanut butter desserts all over again.
I first had it years ago when a coworker (shoutout to Donna, you legend) brought it to an office party. I’ll be honest, it didn’t look flashy. No layers, no sprinkles, no Instagram-ready decorations. But holy heck, that first forkful basically rewired my brain. Soft, buttery peanut butter cake topped with warm, fudge-like icing that soaks into every crack and corner? Sold. I begged her for the recipe, and I’ve been making it ever since… for birthdays, potlucks, breakups, Tuesdays—you name it.
If you’re looking for a cake that feels like a big warm hug and a little bit like you’re five years old again eating peanut butter right off the spoon, this is it.
Why You’ll Love This Peanut Butter Sheet Cake Recipe?
Here’s the deal. You’re getting a big, buttery, peanut-buttery cake with basically zero effort. It’s made in a single sheet pan — meaning no stacking, no piping, no drama. The batter comes together in minutes, and the frosting? You pour it on while the cake’s still warm, letting it melt into the top like a dream. (Seriously, who needs a fancy layered cake when you’ve got melty peanut butter icing dripping down the sides?)
Perfect for feeding a crowd… or just yourself, if you’re having “one of those weeks.” No judgment here.
Ingredient Notes:
Alright, let’s break this masterpiece down:
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All-Purpose Flour: Just your basic everyday flour. Nothing fancy.
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White Sugar: Gives that classic sweetness without overwhelming the peanut butter.
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Baking Soda: Helps the cake puff up into a soft, fluffy dream.
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Milk: Keeps everything tender and moist.
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Eggs: Bind everything together and give a little richness.
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Vanilla Extract: Adds that warm, comforting background note.
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Water, Butter, Vegetable Oil: It sounds odd, but the mix keeps the cake incredibly moist.
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Peanut Butter: The whole reason we’re here, folks. Use creamy peanut butter for that silky texture.
For the Icing:
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Butter + Peanut Butter: Melted together until glossy and glorious.
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Milk: To thin it out just right.
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Vanilla: To round out the flavor.
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Confectioners’ Sugar: For that sweet, creamy fudge finish.
How To Make Peanut Butter Sheet Cake?
Step 1: Preheat and Prepare
Get that oven going at 350°F. Grease up a 10×15-inch baking sheet. Parchment is optional, but your future self doing dishes will thank you.
Step 2: Whisk the Dry Ingredients
In a big ol’ bowl, whisk together your flour, sugar, and baking soda. Nothing complicated here.
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Step 3: Mix the Wet Ingredients
Beat the milk, eggs, and vanilla right into the flour mixture. No need for a separate bowl unless you’re feeling fancy.
Step 4: Make the Liquid Gold
In a saucepan, stir together the water, butter, vegetable oil, and peanut butter over medium heat until it’s all smooth and glossy. Try not to eat it straight from the pan (or do, I’m not your boss).
Step 5: Combine
Pour that peanut butter goodness into your flour mixture and stir until combined. It’s gonna smell ridiculously good already.
Step 6: Bake
Spread the batter evenly into the prepared pan and bake for about 20 minutes, or until a toothpick comes out clean.
Step 7: Frost While Warm
As soon as the cake comes out of the oven, get cracking on the icing. Melt butter and peanut butter together, stir in milk and vanilla, then whisk in the powdered sugar until it’s thick but pourable.
Pour it right over the warm cake and spread it out. The icing will seep into the cake a little and form the fudgy top layer of your dreams.
Storage Options:
Honestly, if this cake lasts long enough to need storing, you deserve an award.
But if you somehow have leftovers, keep them covered at room temp for up to 3 days. If you want it to stay fresher longer, stash it in the fridge — just let it come back to room temp before diving in so the icing softens back up to its fudgy glory.
Variations and Substitutions:
Feeling adventurous? Try these:
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Crunchy Peanut Butter: For those who love a little texture.
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Chocolate Chips: Fold into the batter if you’re chasing that peanut butter cup vibe.
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Different Nut Butters: Almond or cashew butter can totally work here.
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Gluten-Free: Swap in a 1:1 gluten-free flour blend and you’re golden.
What to Serve with Peanut Butter Sheet Cake?
This cake plays real nice with:
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Cold Milk: Duh. Iconic pairing.
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Hot Coffee: Cuts the sweetness perfectly.
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Vanilla Ice Cream: If you’re really going for it (and you should).
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A Sprinkle of Flaky Sea Salt: Trust me, it’s a little fancy, a little genius.
Frequently Asked Questions:
Can I make this ahead of time?
Absolutely! It actually gets even better the next day as the icing soaks into the cake.
Does the frosting have to go on while the cake is hot?
Yes, yes, a thousand times yes. It’s the secret to that perfect fudge-like topping.
Can I freeze it?
Yep! Slice it first, then wrap each square individually. Defrost at room temp when you need a pick-me-up.
And there you have it. The Peanut Butter Sheet Cake that stole my heart (and probably a few waistlines along the way).
Have you ever had a cake do that to you? Drop me a comment and tell me your best “accidentally ate half a sheet cake in one sitting” story — no judgment here.
<Remember it later>
Planning to try this recipe soon? Pin it for a quick find later!
<Remember it later>
Planning to try this recipe soon? Pin it for a quick find later!
Keep the Flavor Coming – Try These:
Peanut Butter Sheet Cake
Ingredients
For the Cake:
- 2 cups all-purpose flour
- 2 cups granulated white sugar
- 1 teaspoon baking soda
- ½ cup whole milk
- 2 large eggs
- 1 teaspoon vanilla extract
- 1 cup water
- ½ cup unsalted butter
- ½ cup vegetable oil
- ½ cup creamy peanut butter
For the Icing:
- ½ cup unsalted butter
- ½ cup creamy peanut butter
- ⅓ cup whole milk adjust as needed
- 1 teaspoon vanilla extract
- 4¾ cups confectioners' sugar
Instructions
Preparation:
- Preheat the oven to 350°F (175°C). Grease a rimmed 10x15-inch baking sheet thoroughly.
Mix Dry Ingredients:
- In a large mixing bowl, whisk together the flour, granulated sugar, and baking soda until well combined. Set aside.
Prepare Wet Ingredients:
- In a separate bowl, beat the milk, eggs, and vanilla extract using an electric mixer set to low speed until smooth and incorporated.
Cook the Peanut Butter Mixture:
- In a medium saucepan over medium heat, combine the water, unsalted butter, vegetable oil, and peanut butter. Stir continuously until the mixture is smooth and fully melted, approximately 5 minutes.
Combine and Bake:
- Gradually stir the warm peanut butter mixture into the flour mixture until a cohesive batter forms. Pour the batter evenly into the prepared baking sheet, spreading it gently with a spatula.
Bake the Cake:
- Bake in the preheated oven for approximately 20 minutes, or until a toothpick inserted into the center comes out clean. Remove from oven and allow the cake to remain warm while preparing the icing.
Prepare the Icing:
- In a separate saucepan, melt the unsalted butter and peanut butter together over medium heat. Stir until smooth. Add the milk and vanilla extract, stirring until incorporated.
Finish the Icing:
- Gradually whisk the confectioners' sugar into the peanut butter mixture until a smooth, spreadable icing forms, typically 3 to 5 minutes.
Frost the Cake:
- Immediately pour the warm icing over the warm cake, using an offset spatula to spread it evenly. Allow the cake to cool completely before slicing and serving.
Notes
I’m Bitty, owner of nodashofgluten.com, where I share simple, delicious recipes for all tastes, including gluten-free. Check out my “About Me” page for more info!
