Peanut Butter Sheet Cake with Peanut Butter Frosting

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The “Double-Nut” Peanut Butter Sheet Cake

This cake is famously paired with a warm frosting that is poured over the cake while it’s still hot, creating a seamless bond between the two layers.

CategoryDetails
Prep Time15 minutes
Bake Time20 minutes
Total Time35 minutes
Yield20–24 servings

🍴 Ingredients

  • The Hot Batter:
    • 2 cups All-purpose flour
    • 2 cups Granulated sugar
    • 1 tsp Baking soda & ½ tsp Salt
    • 1 cup (2 sticks) Unsalted butter
    • 1 cup Water
    • ½ cup Creamy peanut butter
    • 2 Large eggs
    • ½ cup Buttermilk
    • 1 tsp Vanilla extract
  • The Warm PB Frosting:
    • ½ cup (1 stick) Unsalted butter
    • ½ cup Creamy peanut butter
    • 1/3 cup Milk
    • 3 ½ cups Powdered sugar, sifted
    • 1 tsp Vanilla extract

👩‍🍳 Instructions

1. The Dry Base

  • Preheat your oven to 200°C (400°F)—the high heat is key for that quick sheet-cake rise. Grease a 13×18 inch jelly roll pan.
  • In a large bowl, whisk together the flour, sugar, baking soda, and salt.

2. The Boiling Marriage

  • In a medium saucepan, combine the butter, water, and peanut butter. Bring the mixture to a rolling boil, stirring constantly.
  • Pour the boiling mixture over the dry ingredients and stir until smooth.

3. The Finishers

  • Whisk in the eggs, buttermilk, and vanilla. The batter will be quite thin—this is exactly what you want for a sheet cake.
  • Pour into the prepared pan and bake for 20 minutes or until a toothpick comes out clean.

4. The “Second Boil” Frosting

  • About 5 minutes before the cake comes out of the oven, start the frosting.
  • In a saucepan, bring the butter, peanut butter, and milk to a boil. Remove from heat and immediately whisk in the powdered sugar and vanilla until silky smooth.

5. The Hot Pour

  • The Critical Move: Pour the warm frosting over the hot cake the moment it comes out of the oven. Use a spatula to spread it quickly. The frosting will slightly “soak” into the top layer of the cake, creating a fudge-like interface.

The “Crunch” Factor: If you miss the texture of crunchy peanut butter, sprinkle ½ cup of crushed dry-roasted peanuts over the frosting while it’s still wet. It adds a necessary saltiness that cuts through the sugar.

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