## Classic Southern Peanut Butter Sheet Cake
If you want a legendary dessert that feeds a crowd and disappears in minutes, **Peanut Butter Sheet Cake** is an absolute masterpiece. It is the ultimate cousin to the famous Texas chocolate sheet cake, featuring an incredibly moist, tender peanut butter sponge baked in a large jelly roll pan, then smothered in a rich, buttery cooked peanut butter fudge icing while still warm.
It melts in your mouth and delivers a double dose of sweet, salty, nutty perfection!
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### The Culinary Science of Sheet Cake Success
Achieving that iconic, ultra-moist crumb and a poured-on fudge frosting that sets into a glossy glaze comes down to two classic baking techniques:
1. **The Pour-On Hot Frosting Method:** Unlike traditional frostings that are whipped and spread on a cooled cake, sheet cake frostings are cooked on the stovetop and poured directly over the warm cake. As it cools, the hot mixture seeps slightly into the top crumbs, creating a fudgy, melt-in-your-mouth layer.
2. **Buttermilk and Baking Soda:** Using buttermilk provides acidity that reacts with baking soda to create gentle carbon dioxide bubbles, keeping the crumb exceptionally light and tender even with dense ingredients like peanut butter.
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### Ingredients
* **The Peanut Butter Cake:**
* 2 cups all-purpose flour
* 2 cups granulated sugar
* 1 teaspoon baking soda
* 1/2 teaspoon salt
* 1 cup (2 sticks) unsalted butter
* 1 cup water
* 1/2 cup creamy peanut butter (traditional commercial peanut butter like Jif or Skippy works best here for consistent moisture)
* 1/2 cup buttermilk (or whole milk mixed with 1 tsp lemon juice/vinegar)
* 2 large eggs, lightly beaten
* 1 teaspoon pure vanilla extract
* **The Poured Peanut Butter Fudge Icing:**
* 1/2 cup (1 stick) unsalted butter
* 1/4 cup whole milk (or heavy cream)
* 1/3 cup creamy peanut butter
* 1 teaspoon pure vanilla extract
* 3 to 4 cups powdered sugar (sifted, to ensure a smooth glaze)
* *Optional garnish:* 1/2 cup finely chopped roasted peanuts for a delightful crunch on top.
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### Step-by-Step Instructions
#### 1. Mix the Dry Ingredients
1. Preheat your oven to 350°F (175°C). Generously grease and flour a large rimmed baking sheet or jelly roll pan (roughly 12×17 inches or a standard 10×15-inch sheet cake pan).
2. In a large mixing bowl, whisk together the flour, granulated sugar, baking soda, and salt.
#### 2. Melt the Butter and Peanut Butter Base
1. In a medium saucepan over medium heat, combine the 1 cup of butter, water, and 1/2 cup of creamy peanut butter. Bring the mixture to a gentle boil, stirring until completely melted, smooth, and combined.
2. Pour the hot peanut butter mixture directly into your dry flour mixture. Whisk until smooth.
#### 3. Add Wet Ingredients and Bake
1. Whisk in the buttermilk, beaten eggs, and vanilla extract until a uniform, smooth batter forms.
2. Pour the batter evenly into your prepared sheet pan.
3. Bake at **350°F (175°C) for 20 to 25 minutes**, or until a toothpick inserted into the center comes out clean and the edges are lightly golden.
#### 4. Make the Fudge Icing (Right as Cake Finishes)
1. About 5 minutes before your cake comes out of the oven, start the icing. In a medium saucepan, melt the 1/2 cup of butter and the milk together over medium heat. Stir in the peanut butter until smooth, then remove from heat.
2. Whisk in the vanilla extract and gradually add the sifted powdered sugar, whisking vigorously until completely smooth and thick (like a pourable fudge glaze).
#### 5. Pour and Set
1. As soon as the cake comes out of the oven and is **still piping hot**, pour the warm peanut butter icing evenly all over the top. Use an offset spatula to gently guide it to the edges.
2. If using chopped peanuts, scatter them evenly across the top before the icing sets.
3. Allow the cake to cool completely at room temperature so the fudge glaze firms up into a shiny, decadent layer. Slice into squares and serve!
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### Pro-Tips for Success
* **Don’t Overbake:** Because sheet cakes are relatively thin, keep a close eye on the timer so the edges don’t dry out.
* **Serving Suggestion:** This cake is intensely rich and sweet on its own, but serving a square with a scoop of vanilla bean ice cream or a cold glass of milk takes it straight to heaven.
Are you baking this peanut butter sheet cake for a party, a potluck, or just to satisfy a serious sweet tooth at home?
