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Insane Chocolate and Peanut Butter Sheet Cake | BakeThenEat.com
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Insane Chocolate and Peanut Butter Sheet Cake

A classic rich chocolate sheet cake topped with peanut butter cream cheese frosting with an insane amount of peanut butter candy thrown at it!
Prep Time25 mins
Cook Time55 mins
Total Time1 hr 20 mins
Course: Cake
Cuisine: American
Author: Emma


For The Cake

  • 400 grams granulated sugar (2 cups)
  • 210 grams Plain flour All Purpose, (1 and 3/4 cup)
  • 60 grams unsweetened cocoa powder (3/4 cup)
  • 1 and 1/2 teaspoons baking powder
  • 1 and 1/2 teaspoons baking soda
  • 1 teaspoon fine sea salt
  • 2 large eggs at room temperature
  • 240 millilitres milk at room temperature (1 cup)
  • 120 milliliters vegetable oil (1/2 cup)
  • 2 teaspoons vanilla extract
  • 240 milliliters boiling water (1 cup)

For The Frosting & Decoration

  • 170 grams unsalted butter at room temperature (1 and 1/2 sticks)
  • 125 grams smooth peanut butter (1/2 cup)
  • 225 grams Icing sugar Confectioners sugar - sieved, (2 cups)
  • 200 grams full fat cream cheese - just softened (8 ounces)
  • 30 mini peanut butter cups (The tiny ones with no wrapper on them)
  • 90 grams peanut butter m&m's (2 ounces)
  • 43 grams peanut butter Reese's Pieces (1.5 ounces)


The Cake

  • Preheat your oven to 180C / 350F / Gas mark 4 and lightly grease a 9 x 13 inch tin that is at least 2 inches deep. Then place to one side.
  • In a large mixing bowl add in the sugar, flour, cocoa powder, baking powder, baking soda and salt. Give it a little whisk to mix everything together.
  • Switch the kettle on to boil and while it is heating carry on with the cake.
  • Add in the eggs, milk, vegetable oil and vanilla extract and give everything a good mix. The batter will be thick but this is fine the boiling water will thin it right down.
  • Pour in the boiling water and mix it in as quickly and safely as you can. The batter will be very thin but this is what you want. Pour it immediately into your prepared baking pan and pop it in the centre of your hot oven.
  • The original recipe states this cake bakes in 30 to 35 minutes. I checked it at this point and it was no where near done. In my oven this cake took between 50 to 60 minutes.
  • By all means check your cake at 30 minutes, and keep going back to every 5 to 10 minutes to check for readiness. Once a skewer comes out clean from the centre this cake is done. Like I said in my oven it to somewhere between 50 to 60 minutes.
  • Once baked take the cake out of the oven and allow the cake to fully cool down in its tin. At least 1 hour.
  • Once the cake is fully cool, turn the pan upside down onto a wire rack and the cake should just fall onto the rack. Turn it back over and your cake is ready to frost.

The Frosting

  • Beat your butter with an electric mixer or a stand mixer until it is pale and fluffy.
  • Add in the peanut butter and again mix for a couple of minutes until it is smooth and creamy.
  • Slowly add in the icing sugar with the beater on low (so as not to create a dust cloud!) Beat until everything is well mixed together.
  • Add in the cream cheese and mix for a minute or two until it is well combined. If you are in the UK please check above for a link on working with cream cheese if you live in the UK! It will stop your frosting from going all runny and gloopy!
  • Take 20 of your mini peanut butter cups and gently press them into the top of the cake at regular initials. The idea is when the cake is cut each piece will have one in the middle. I found I got 5 across and 4 down, giving me 20 equal squares for serving.
  • First off you will need to do a crumb layer. Take about a 3rd of your frosting and gently spread it across your cake, don't worry if it looks full of crumbs we will cover this all up.
  • Once that is done pop the cake in the fridge for 10 to 15 minutes to firm up that layer.
  • Once that is done the crumb layer will act as a barrier and you will be able to frost your cake normally. Spread the rest of the frosting evenly across your cake.
  • Take your remaining 10 mini peanut butter cups and cut them in half. Take them, your peanut butter m&m's and Reese's Pieces and scatter them all across the top of your cake.
  • Because of the frosting this cake will need to be kept in the fridge, also it cuts better when cold. But bring it back up to room temperature before serving. Kept in the fridge in an airtight container this cake keeps well up to 5 days.