Ingredients
1cupunsalted butter
1cupwater
½cupnatural cocoa powder,unsweetened, not Dutch process
2cupsall purpose flour,spoon & leveled
1tspbaking soda
¼tspsalt
2large eggs,at room temperature
1cupgranulated sugar
½cuplight brown sugar,packed
2tsppure vanilla extract
½cupbuttermilk,at room temperature
1½cupscreamy peanut butter,do not use natural style
½cupunsalted butter,softened to room temperature
3cupsconfectioner’s sugar
½cupheavy cream,or half and half, or whole milk
1tsppure vanilla extract
pinchsalt
½cupcreamy peanut butter,melted, for drizzling
1cuppeanut butter cups,chopped
mini chocolate chips
peanut butter chips
chocolate sprinkles
Preparation
Preheat oven to 350 degrees F. Generously grease a 12×17-inch half sheet/jelly roll pan. Set aside.
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 aside.
In a large bowl, whisk the flour, baking soda, and salt together. Pour the warm chocolate/butter mixture on top, then slowly whisk together until combined. It will be very thick.
Whisk the eggs, granulated sugar, and brown sugar together in a medium bowl. The mixture will be thick.
Whisk in the vanilla until combined, then pour into the chocolate batter and whisk until combined. Finally, whisk in the buttermilk.
Pour the chocolate batter into the sheet pan.
Bake for 15 to 20 minutes. If a toothpick comes out clean, the cake is done. If not, continue baking.
Remove cake from the oven and set the pan on a wire rack. Allow the cake to cool completely in the pan before frosting. The refrigerator helps speed things up.
Using a handheld or stand mixer fitted with a whisk attachment, beat softened butter and peanut butter together on medium-high speed for 2 minutes until completely smooth and creamy.
Add the confectioners’ sugar, cream, vanilla extract, and salt. Beat on low speed for about 20 seconds, then gradually increase to high speed.
Beat on high for 1 minute until combined and the frosting is fluffy. Taste and add more salt if needed. To thicken, add more confectioners’ sugar; and to thin, add more cream.
Spread frosting all over cooled cake, then top with toppings. Slice and serve.
Cover leftovers tightly and store them in the refrigerator for up to 5 days. It’s so good cold!
