Chocolate Peanut Butter Cake for a crowd

A sinfully delicious Chocolate Peanut Butter cake to celebrate my new cookbook, TONIGHT! A killer combination of rich Chocolate Cake smothered with fluffy peanut butter frosting, topped with peanut butter cups, it’s decadent and perfect for gatherings as it will easily serve 20 to 25 people.

Layer cakes for a crowd are a logistical nightmare!

Today’s cake is dedicated to everyone who has tried to cut a towering 4 layer cake into 30 slices to share with co-workers. It’s impossible!!

Enter – slab cakes. A name commonly used for single layer cakes baked in rectangle pans, these are the perfect solution for a cake to serve many that’s easier to construct than layer cakes, more fun to decorate (larger canvas to play with), and easier to transport too (no Leaning Tower of Pisa situation).

Bonus: higher cake-to-frosting ratio per person. It matters!

Today’s slab cake involves the never-fail combination of peanut butter and chocolate, decorated with casual abundance (ie no stress). It looks like a Jackson Pollock – but better, because it’s edible!

Ingredients in this Chocolate Peanut Butter Cake

This cake is made with my classic, forever Chocolate Cake (beautiful chocolatey flavour, a soft moist crumb and ridiculously simple to make – no electric beater required), fluffy peanut butter frosting and decorations (Reece’s peanut butter cups, chocolate and peanut butter drizzle plus chopped nuts). Abundance!

The chocolate cake

Here’s what you need for the chocolate cake.

• Flour – just plain / all purpose flour. No need to use pricier cake flour (actually makes the crumb too damp, I find).

• Cocoa powder – regular, unsweetened cocoa powder (unsweetened is the default here in Australia), not hot chocolate powder (sweetened). The cake works with dutch processed cocoa powder (pricier, with more intense chocolate flavour) but it doesn’t improve it by a noticeable amount so it’s not worth using for this cake, in my opinion.

• Coffee powder (OPTIONAL!) – This unusual sounding ingredient in a chocolate cake is a little secret trick to enhance the flavour of chocolate in cakes. You can’t taste coffee at all! And it’s just a small amount. There’s no need to hunt down an expensive brand, just any brand is fine. Just be sure to get the dissolvable granules (ie that dissolve when you add hot water), not the ground coffee beans that is used for plungers, filters and coffee machines (does not dissolve).

  Substitute with hot freshly brewed coffee instead of boiling water.

• Baking powder and baking soda (bi-carb soda) – These both make cakes, muffins etc rise but have different effects on different batters. As a general rule, baking soda is 3x stronger than baking powder. For this cake, a combination of both makes the cake rise so it has a relatively flat surface (rather than a dome) and the crumb is lovely and light.

  Substitute – Just use baking powder. The cake rises slightly less but no one will notice unless you’re a recipe control-freak like, say, me, who will test versions of the cake and line them up side by side to compare.😂

• Eggs – This recipe calls for “large eggs” which are eggs sold in cartons labelled as “large eggs”. The weight for a 12 egg carton is 600 – 660g (24 oz), with each egg weighing 55 – 55g / 2 oz in the shell. Unlike most recipes, there is no need to bring the eggs to room temperature because boiling water is added into the batter which brings the temperature of fridge-cold ingredients up to ensure everything combines together properly!

• Sugar – Just regular white sugar (granulated sugar). Caster sugar / superfine sugar ist fine to use here too but not necessary. Don’t use brown sugar, makes the cake too damp and alters the flavour.

• Salt – This recipe calls for 1 whole teaspoon of salt which I know sounds like a lot but it really helps bring out the chocolate flavour and does NOT make it taste salty at all! Be sure to use cooking salt (sold labelled as such) or kosher salt (US). If you only have table salt (the fine, sand-like salt) use 3/4 teaspoon and if you only have fancier sea salt flakes, use 1 1/2 teaspoons.

• Milk – Full fat cow milk is best though low fat works too. And in my travels, I’ve discovered / read from readers that non-animal milks work as well, including soy, almond and oat milk.

• Oil – Any neutral flavoured oil, like vegetable oil, canola, rapeseed, grapeseed or sunflower oil can be used. This recipe uses oil rather than butter as the fat and this is partly what makes the cake so moist and gives it excellent shelf life (it stays fresh for 5 days). Rule of thumb for baking – butter gives things flavour but oil keeps things moist! (Reason: butter hardens when cold, oil stays liquid).

• Vanilla extract – For flavour enhancement. It doesn’t make the cake vanilla-forward, it compliments the chocolate flavour.

• Boiling water – This makes the chocolate flavour from the cocoa bloom! It also warms up fridge-cold ingredients (eggs and milk) to ensure everything combines together thoroughly. So nice to have a cake recipe that does call for anything to be “at room temperature”!

The peanut butter frosting

The frosting is a buttercream frosting which is whipped until beautifully light and fluffy with a good amount of peanut butter!

• Peanut butter – I use peanut butter spread for this recipe which has sugar and salt added to it, rather than pure, natural peanut butter which I use for things like Satay Peanut Sauce. If you only have natural peanut butter, you will need to use less because it’s runnier (see recipe notes).

• Unsalted butter – Softened to room temperature so it can be whipped into a fluffy frosting. Don’t let it get too soft and sloppy else your frosting will be too! Technically in baking terms, “softened butter” should be 17°C/63°F – firmer than you think! 🙂 This is soft enough to whip into creamy fluffiness but firm enough so it doesn’t turn frosting into slop.

• Soft icing sugar / powdered sugar – If you’re in Australia, be sure to get soft icing sugar which is used for fluffy frostings like this, NOT pure icing sugar which is used for icings that set hard like royal icing (used for piping decorations on Gingerbread Men etc). If you are not in Australia, you don’t need to worry about this as soft v pure icing sugar options seems to be a uniquely Australian thing.

• Vanilla – For flavour.

• Pinch of salt – To bring out the flavours in the frosting.

TOPPINGS – recommended but optional!

You could make this without any toppings at all and I’d still scoff it down. But with the toppings, it takes it over the top into Outrageous Land which I’m always happy to be in! Pick and choose as you please, what you like and what suits your budget. 🙂

Reece’s peanut butter cups (optional) – some regular miniature ones and some mini, mini ones, some chopped, some kept whole! Yes this adds that extra “wow” factor to this cake but I would not hesitate to make this cake without.

1. Melted chocolate drizzle – Just chocolate chips or melts, melted with a little cream so it doesn’t solidify when it cools.

2. Melted peanut butter – Literally just peanut butter melted in the microwave turns it into perfect drizzle-able form! (Is that a word??)

3. Chopped peanuts (oops, forgot a photo) – For sprinkling! I like to use salted peanuts.

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How to make Chocolate Peanut Butter Cake

Make the cake first. It will take a good couple of hours to fully cool which is essential before slathering on the frosting (hot cake = melted frosting = 😭). Speed things up by popping it in the fridge.

1. The cake

The cake part is so easy – just one bowl and a wooden spoon! (Well, whisk. 🙂 )

1. Whisk dry – Sift the flour, cocoa, baking powder and baking soda into a bowl. Add the sugar and salt, then whisk to combine.

2. Add wet – Add the egg, oil, milk and vanilla, then whisk.

3. Boiling water & coffee – Add the coffee powder then pour in the hot water (so the instant coffee powder dissolvers). Whisk well to combine.

4. Heads up: the batter is VERY thin!

5. Pour the batter into a 23 x 33cm / 9 x 13″ pan lined with paper.

6. Bake for 45 minutes or until a skewer inserted into the centre comes out clean. Then fully cool on a rack before frosting and decorating!

2. DECORATING

1. Spread the frosting on the cake.

2. Drizzle – Melt the chocolate with the cream (15 second bursts in the microwave). Heat the peanut butter until it’s runny enough to drizzle. Let them both cool for a few minutes then randomly drizzle across the cake. Use most now and reserve some for drizzling again once the other toppings are on.

3. Peanut butter cups – Randomly scatter the peanut butter cups across the surface. I cut the miniature ones in half and keep the mini, mini ones whole.

4. Sprinkle & drizzle again! Then sprinkle the entire surface with finely chopped peanuts and a another drizzle of chocolate and peanut butter (I TOLD YOU THIS WAS OUTRAGEOUS!!).

Stand back and admire your edible Jackson Pollock!

Matters of serving and storing

Another side benefit of a slab cake compared to towering layers cakes is that there is no need to refrigerate for a bit to stabilise it before cutting. This cake is ready to go the moment you finish that last drizzle of chocolate!

Cut slices to whatever size you desire, and because we’re generous with toppings the slices don’t need to be that large to still be indulgent! 20 slices is a nice size (6.5 x 5.75cm / 2.25 x 2.6″) – cut 5 on the long side then 4 on the short side. Though it can easily serve 25.

Store it in the fridge though always bring to room temperature before serving because the buttercream frosting will go hard. The cake will stay fresh for 5 days so it’s got a terrific shelf life.

Enjoy! – Nagi x

PS Today’s photos were taken by Rob Palmer whom I hope to be working with on a regular basis from hereon as I look to get more sleep and maintain my focus on the recipe development, testing, post writing and video making side. One less thing to do – and, well, you know. He’s a pro. I love working with Rob!

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Watch how to make it

Life of Dozer

When Dozer was on the cover of Australia’s most respected food paper – but he just wanted to get to a pile of chicken on the bench!

And he was in the paper too.

I have a feeling the editor never imagined running an edition of Good Food with a dog so prominently featured. 😂

This article was a story relating to my second cookbook, TONIGHT, which I surprised you with in my last post. Now that you know about it, I can start sharing cheeky Dozer behind-the-scenes photos from the making of Tonight! Here’s the first – Dozer disrespecting my work, trampling all over the proofs.

Impossible to get mad at that face!