Chocolate Sheet Cake with Peanut Butter Frosting

Fudgy, beyond rich chocolate sheet cake topped with the creamiest peanut butter frosting. Feeds a crowd! I encourage you to read the full recipe and the recipe notes before beginning so you’re completely prepared.

Ingredients

• 1 cup (16 Tbsp; 226g) unsalted butter
• 1 cup (240ml) water
• 1/2 cup (41g) unsweetened natural cocoa powder (not dutch-process)
• 2 cups (250g) all-purpose flour (spooned & leveled)
• 1 teaspoon baking soda
• 1/4 teaspoon salt
• 2 large eggs, at room temperature
• 1 cup (200g) granulated sugar
• 1/2 cup (100g) packed light brown sugar
• 2 teaspoons pure vanilla extract
• 1/2 cup (120ml) buttermilk, at room temperature*

Peanut Butter Frosting

• 1 and 1/2 cups (405g) creamy peanut butter (do not use natural style)
• 1/2 cup (8 Tbsp; 113g) unsalted butter, softened to room temperature
• 3 cups (360g) confectioners’ sugar
• 1/2 cup (120ml) heavy cream, half-and-half, or whole milk*
• 1 teaspoon pure vanilla extract
• pinch salt
• optional: 1/2 cup (135g) melted creamy peanut butter and 1 cup chopped peanut butter cups

Instructions

1. Preheat oven to 350°F (177°C). Generously grease a 12×17-inch half sheet/jelly roll pan. Set aside.
2. Heat the butter, water, and cocoa powder together in a large saucepan over medium heat. Whisk constantly until the butter has melted and everything is smooth and combined. Set