Chocolate Sheet Cake with Creamy Peanut Butter Frosting

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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*
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

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