Chocolate Peanut Butter Sheet Cake

Introduction

Hi, I’m Linda. After ten years of baking for my blog, school bake sales, church potlucks, and more birthday parties than I can count, one thing is clear to me. The cake that disappears first is almost never the fancy layered one. It’s the sheet cake.

This Chocolate Peanut Butter Sheet Cake is the one I bring when I need a sure thing. The chocolate cake is soft and tender, and it bakes in about 20 minutes. While the cake is still warm, you spread a layer of creamy peanut butter over it, then pour warm chocolate fudge frosting on top. The peanut butter melts a little into the cake and sets into a layer that tastes like a peanut butter cup.

The first time I made it, I used a pan that was too small and the batter spilled over in my oven. My kitchen smelled like burnt chocolate for two days. I’ll show you how to avoid that, along with the other tricks I’ve picked up over the years.

If you love this flavor combo, you’ll also want to try my layered chocolate cake with peanut butter frosting for special occasions.

Ingredients for chocolate peanut butter sheet cake including flour, cocoa powder, peanut butter, butter, buttermilk, and eggs

Essential Ingredients

For the chocolate cake:

2 cups (250 g) all-purpose flour
2 cups (400 g) granulated sugar
1 teaspoon baking soda
½ teaspoon fine salt
1 cup (226 g) unsalted butter
1 cup (240 ml) water or hot brewed coffee
¼ cup (25 g) unsweetened cocoa powder
½ cup (128 g) creamy peanut butter
½ cup (120 ml) buttermilk, room temperature
2 large eggs, room temperature
1 teaspoon pure vanilla extract

For the peanut butter layer:

¾ cup (190 g) creamy peanut butter

For the chocolate fudge frosting:

½ cup (113 g) unsalted butter
⅓ cup (30 g) unsweetened cocoa powder
6 tablespoons whole milk
4 cups (480 g) powdered sugar, sifted
1 teaspoon vanilla extract
½ cup chopped roasted peanuts, for topping

A digital kitchen scale makes a real difference here. Measuring flour by weight is the easiest way to keep this cake moist and not dry. The King Arthur Baking ingredient weight chart is the reference I use when I convert recipes.

Alternative Ingredients

Buttermilk: No buttermilk? Stir 1½ teaspoons of lemon juice or white vinegar into ½ cup of milk and let it sit for 5 minutes.

Peanut butter: Use a regular no-stir brand like Jif or Skippy. Natural peanut butter separates and can make the top layer oily. Almond butter or sunflower seed butter work if you need a nut-free option for a school event.

Cocoa powder: Natural cocoa is what this recipe is built on, because it reacts with the baking soda. If you only have Dutch-process cocoa powder, add ¼ teaspoon of baking powder to the batter.

Gluten-free: A 1-to-1 gluten-free flour blend with xanthan gum works well. The cake comes out slightly more delicate, so let it cool fully before you slice.

Dairy-free: Use plant-based butter sticks, oat milk with vinegar in place of buttermilk, and oat milk in the frosting.

Chocolate peanut butter sheet cake with fudge frosting and chopped peanuts in a sheet pan

Step-by-Step Directions

1. Prep the pan. Heat your oven to 350°F (175°C). Grease a 15×10-inch jelly roll pan or a half sheet pan (18×13 gives you a thinner cake). Do not use a 9×13 pan. That’s the mistake that made my oven a mess.

2. Mix the dry ingredients. In a large bowl, whisk the flour, sugar, baking soda, and salt.

3. Make the chocolate base. In a saucepan over medium heat, combine the butter, water or coffee, cocoa, and ½ cup peanut butter. Stir until it boils and looks smooth. Pour this over the dry ingredients and stir until combined.

4. Add the wet ingredients. Whisk the buttermilk, eggs, and vanilla in a small bowl. Add to the batter and mix just until smooth. A hand mixer or stand mixer on low speed works, but a whisk is fine. The batter will be thin. That’s normal.

5. Bake. Pour into the pan and spread evenly. Bake for 20 to 24 minutes, until a toothpick in the center comes out with a few moist crumbs.

6. Add the peanut butter layer. While the cake is hot, drop spoonfuls of the ¾ cup peanut butter over the top. Wait 2 minutes, then spread it gently with an offset spatula. It melts into a smooth layer.

7. Make the frosting. About 5 minutes before the cake is done, melt the butter in a saucepan. Add the cocoa and milk and bring to a gentle boil. Take it off the heat and whisk in the powdered sugar and vanilla until glossy.

8. Frost and finish. Pour the warm frosting over the peanut butter layer and spread it quickly. Sprinkle with chopped peanuts right away so they stick. Let the cake cool at least 1 hour before slicing.

Pro Tips

Use hot coffee in place of the water. You won’t taste coffee, but the chocolate flavor gets deeper. This is my favorite trick for any chocolate cake, and I use it in my chocolate buttermilk cake too.

Make the frosting while the cake bakes. The frosting needs to go on warm, or it gets stiff and tears the peanut butter layer.

Bring the eggs and buttermilk to room temperature. Cold ingredients hit the hot chocolate mixture and the batter can turn lumpy.

Don’t overbake. Sheet cakes are thin, so 2 extra minutes can dry them out. Start checking at 20 minutes.

A good light-colored aluminum pan bakes more evenly than a dark one. If you’re shopping for the best baking pans, a heavy half sheet pan like Nordic Ware is worth it. You’ll use it for cookies and sheet pan dinners too.

FAQs

Can I make this cake ahead of time?
Yes. It actually tastes better the next day. Cover it and keep it at room temperature for up to 2 days or in the fridge for up to 5 days.

Can I freeze chocolate peanut butter sheet cake?
Yes. Freeze cut squares on a tray, then wrap each one in plastic and store in a freezer bag for up to 3 months. Thaw in the fridge overnight.

Why did my frosting turn grainy?
Usually the powdered sugar wasn’t sifted, or the frosting boiled too long. Keep it at a gentle simmer and whisk well.

Can I use crunchy peanut butter?
In the cake batter, stick with creamy. For the top layer, crunchy works if you like extra texture.

How do I get clean slices?
Chill the cake for 20 minutes, then use a long sharp knife. Wipe it with a warm damp towel between cuts.

Recipe Info

Detail	Info
Prep Time	20 minutes
Cook Time	22 minutes
Cooling Time	1 hour
Total Time	1 hour 42 minutes
Servings	24
Yield	One 15×10-inch sheet cake
Difficulty	Easy

Why You’ll Love This Recipe

It feeds a crowd from one pan, so it’s perfect for birthdays, potlucks, and holiday parties. There’s no stacking, no leveling, and no crumb coat. The batter comes together in one bowl and one saucepan, so cleanup is quick. And the chocolate and peanut butter flavor makes kids and adults happy at the same time.

What Makes This Recipe Unique

Most chocolate sheet cakes only use peanut butter in the frosting. This one puts it in three places: inside the batter, as a melted middle layer, and as chopped peanuts on top. Peanut butter in the batter keeps the cake moist for days. The warm layer on top sets like the inside of a peanut butter cup. It’s based on the classic Texas sheet cake method, but with much more peanut butter flavor.

Key Features

Ready to serve in under 2 hours
Moist cake that stays soft for up to 5 days
Budget-friendly pantry ingredients
Easy gluten-free, dairy-free, and nut-free swaps
Freezer-friendly for easy meal planning and parties

Nutrition Facts (per serving, 1 of 24)

Nutrient	Amount
Calories	390 kcal
Total Fat	20 g
Saturated Fat	9 g
Cholesterol	45 mg
Sodium	230 mg
Total Carbohydrates	48 g
Sugars	37 g
Fiber	2 g
Protein	6 g

Nutrition values are estimates and will change with the brands you use.

You’ll Also Love

Looking for more chocolate desserts? Take a look at our full collection of easy homemade desserts, where you’ll find cakes, brownies, and no-bake treats for every occasion. For more sheet cake ideas, the Allrecipes cake collection has hundreds of reader-tested recipes, and Food Network’s dessert recipes are great for party inspiration.

Conclusion

This Chocolate Peanut Butter Sheet Cake has been my go-to crowd pleaser for years, and I hope it becomes yours too. It’s simple, it’s quick, and it tastes like you spent all day on it. Use the right size pan, make your frosting while the cake bakes, and put it on while everything is still warm. That’s really all there is to it.

If you make this recipe, leave a comment and a star rating below. I read every one, and I’d love to hear how yours turned out.

Happy baking,
Linda

Chocolate Peanut Butter Sheet Cake

A moist, fudgy chocolate sheet cake with a melted peanut butter layer and warm chocolate fudge frosting, topped with chopped roasted peanuts. One pan feeds a crowd.

★★★★★ By Linda | Course: Dessert | Cuisine: American

Prep20 min

Cook22 min

Total1 hr 42 min

Servings24

Ingredients

For the Chocolate Cake

2 cups (250 g) all-purpose flour
2 cups (400 g) granulated sugar
1 teaspoon baking soda
½ teaspoon fine salt
1 cup (226 g) unsalted butter
1 cup (240 ml) water or hot brewed coffee
¼ cup (25 g) unsweetened cocoa powder
½ cup (128 g) creamy peanut butter
½ cup (120 ml) buttermilk, room temperature
2 large eggs, room temperature
1 teaspoon pure vanilla extract

For the Peanut Butter Layer

¾ cup (190 g) creamy peanut butter

For the Chocolate Fudge Frosting

½ cup (113 g) unsalted butter
⅓ cup (30 g) unsweetened cocoa powder
6 tablespoons whole milk
4 cups (480 g) powdered sugar, sifted
1 teaspoon vanilla extract
½ cup chopped roasted peanuts

Instructions

Heat the oven to 350°F (175°C). Grease a 15×10-inch jelly roll pan or an 18×13-inch half sheet pan.
In a large bowl, whisk the flour, sugar, baking soda, and salt.
In a saucepan over medium heat, combine the butter, water or coffee, cocoa, and ½ cup peanut butter. Bring to a boil, stirring until smooth, then pour over the dry ingredients and stir.
Whisk the buttermilk, eggs, and vanilla together. Add to the batter and mix just until smooth. The batter will be thin.
Pour into the pan and bake for 20 to 24 minutes, until a toothpick comes out with a few moist crumbs.
While the cake is hot, drop spoonfuls of ¾ cup peanut butter over the top. Wait 2 minutes, then spread gently with an offset spatula.
For the frosting, melt the butter, add the cocoa and milk, and bring to a gentle boil. Remove from heat and whisk in the powdered sugar and vanilla until glossy.
Pour the warm frosting over the peanut butter layer, spread quickly, and sprinkle with chopped peanuts. Cool at least 1 hour before slicing.

Linda’s Notes

Do not use a 9×13 pan, the batter will overflow. Make the frosting while the cake bakes so it goes on warm. Hot coffee in place of water gives a deeper chocolate flavor. Store covered at room temperature up to 2 days, in the fridge up to 5 days, or freeze squares up to 3 months.