Description

This rich and decadent Chocolate Peanut Butter Cake is perfect for serving a large crowd of 20 to 25 people. Featuring a moist chocolate cake base infused with coffee for enhanced flavor, paired with a smooth and creamy peanut butter frosting, and topped with peanut butter cups and chopped salted peanuts for a delightful crunch. Easy to prepare with straightforward ingredients, this cake is a crowd-pleaser ideal for celebrations and gatherings.

Ingredients

Scale

Dry Ingredients

1 3/4 cups plain/all-purpose flour
3/4 cup unsweetened cocoa powder
1 1/2 tsp baking powder
1 1/2 tsp baking soda (bi-carb soda)
2 cups white sugar (or caster/superfine sugar)
1 tsp cooking/kosher salt

Wet Ingredients and Flavorings

2 large eggs
1 cup milk (low or full fat)
1/2 cup vegetable oil (or other plain flavored oil like canola, grapeseed, rapeseed, sunflower)
2 tsp vanilla extract
2 tsp instant coffee powder (optional)
1 cup boiling water

Frosting and Toppings

250g / 2 sticks unsalted butter, softened
4 cups (500 g) soft icing sugar / powdered sugar, sifted
1/2 cup (120 g) smooth peanut butter (spread, not pure)
1/4 tsp cooking/kosher salt
1 tbsp milk
1/2 cup chocolate chips or melts (semi-sweet)
2 tbsp cream (thickened/heavy, not low fat)
3 tbsp peanut butter, warmed to runny
120g / 4 oz mini Reece’s Peanut Butter Cups
10+ miniature Reece’s Peanut Butter Cups, halved
1/4 cup salted peanuts, finely chopped

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Instructions

Preheat the Oven: Preheat your oven to 180°C (350°F) or 160°C if using a fan oven. Preparing the oven in advance ensures it reaches the right temperature for even baking.
Prepare the Cake Pan: Grease a 23 x 33 cm (9 x 13 inches) metal cake pan with butter. Line the pan with baking paper, leaving an overhang on the sides to make lifting the cake out easier. You can use round pans, but adjustments may be needed.
Mix Dry Ingredients: In a large bowl, sift together the flour, cocoa powder, baking powder, baking soda, sugar, and salt. This ensures they are well combined and aerated for a lighter cake texture.
Combine Wet Ingredients: In another bowl, whisk together the eggs, milk, vegetable oil, vanilla extract, and the optional instant coffee powder until smooth and fully incorporated.
Combine Wet and Dry Mixtures: Gradually add the dry ingredients to the wet ingredients, mixing until just combined. Carefully pour in the boiling water last and gently stir to blend; this step helps to ‘bloom’ the cocoa, enhancing the chocolate flavor and resulting in a moist cake batter.
Bake the Cake: Pour the batter into the prepared cake pan and bake for approximately 45 minutes or until a skewer inserted into the center comes out clean. Remove from oven and allow to cool completely in the pan before frosting.
Prepare the Peanut Butter Frosting: Beat the softened butter until creamy. Gradually add the sifted icing sugar, then mix in the smooth peanut butter, salt, and milk. Beat until light and fluffy.
Make Chocolate Ganache Topping: Melt the chocolate chips with cream over a double boiler or microwaving in short bursts, stirring until smooth. Stir in the warmed peanut butter until combined and silky.
Assemble the Cake: Once the cake is fully cooled, spread the peanut butter frosting evenly over the top. Drizzle or spread the chocolate peanut butter ganache over the frosting layer.
Decorate: Garnish the cake with whole mini Reece’s Peanut Butter Cups, halved miniature cups, and sprinkle with finely chopped salted peanuts for a crunchy finish.

Notes

Using instant coffee powder is optional but recommended to intensify the chocolate flavor without adding a coffee taste.
For round pans, baking time may vary; keep an eye on the cake and test with a skewer.
Sifting the cocoa powder and icing sugar helps prevent lumps, ensuring smooth batter and frosting.
Use spreadable peanut butter rather than pure nut butter for best texture in frosting.
Boiling water in the batter helps to extract the cocoa’s rich flavor fully.