RICH Chocolate Sheet Cake For Celebrations!

Chocolate Sheet Cake

This sheet cake is a deliciously rich, chocolate and peanut butter cake that requires just a bowl and a whisk to make. I smother it with my favourite ever chocolate sour cream frosting that you've got to try at least once (and I promise it won't be the last time!). This is a pushy recipe Dear Reader!

Sheet cakes are one of the easiest cakes to make and are perfect for parties and birthdays. They're easy to transport in the tin and can feed so many people. And the frosting layer is almost as thick as the cake but is light and fluffy! They're also freezer friendly so that you can pop the whole thing in the freezer until you need it and they're super easy to serve up!

Why This Chocolate Sheet Cake is PERFECT for Celebrations!

Chocolate Sheet Cake

1 - This is a very light, moist and chocolatey cake - it's rich too so you don't need to serve big slices. Making as a sheet cake which makes it easier to transport as you just take it in the baking tin.

2 - This sheet cake recipe is for a 20x30cm/ 8x12 inch tin that feeds 20 people decent sized squares. I used a lamington tin. If you need to feed more you can double it if you have a 45x30cm or 17x12 inch tin.

3 - You can make this cake one or two days before and it will stay moist or you can make it a few weeks ahead and store it in the freezer. You can also make it fresh, just make sure to cool it completely before icing and keep it in the tin to transport and serve. It can be quite delicate to slice when it's fresh.

4 - I used Reese's peanut butter chocolate chips (available from the supermarket) and Callebaut 811 dark chocolate.

Chocolate Sheet Cake

5 - Finely chopping the chocolate disperses it more evenly through the cake. If you leave the chocolate as chips, toss them in 3 tablespoons of the flour cocoa mix from step 1 and then fold them in. The flour prevents the chocolate chips from sinking to the bottom of the cake once baked.

6 - If there are nut allergies present this can be made into a plain chocolate cake (just omit the peanut butter dollops and replace PB chips with regular chocolate).

7 - I cut out the letters using fondant but also found that Ikea sells alphabet letter cookies in their food section!

Chocolate Sheet Cake

When Monica's partner Marco was having a birthday recently I asked her what I could buy him and she suggested that the best present would be making his birthday cake (because Marco loves sweets, rum and beer and we figured he would be getting lots of bottles of rum already from friends). I love making cakes for friends and last year I made him a beeramisu cake but this time it was a significant birthday and there would be a lot more people so we needed a cake that would feed a crowd. Enter the sheet cake!

Before his birthday I sat down and quizzed Marco about his favourite flavours over dinner. He chose chocolate and peanut butter and he mentioned that he also likes cream cheese frosting too. That icing requires refrigeration and I know that Monica's fridge is always full so I didn't want to take up any extra room so I decided to top it with my favourite icing, the chocolate sour cream frosting. I will literally sit down and eat this by the spoonful it's that delicious.

Chocolate Sheet Cake

Marco's party was at 2pm which is a time that Monica prefers to entertain. She likes that time because it means that people won't expect a big meal but Monica is a feeder as am I so I know that there will also be food available too. She was making all of Marco's favourite things: a tuna pasta salad, capsicum salad and meatballs. I had actually made two of these cakes - one to photograph and cut up and one that was fully intact. The one cake would have been enough to feed the crowd of 20 but I couldn't give him a cake with slices cut out of it.

The only problem was that when we arrived at their house it was bucketing down with rain. This rain was not a light sprinkle, it had weight to it and fell in heavy, fat drops at a fast pace. And while I had covered the cakes with cling film and parchment, that would be no match for the rain and the walk from the car to the house as we had to walk down the side entrance with slippery tiles. Was it bad that I pictured slipping on them and then thinking, "Well this will make for a funny anecdote on the blog"?

I texted Monica that we were there but hiding out in the car. After a while the rain got a little lighter and we quickly scurried inside with the cakes (without falling). We ate food, watched a video of memories and messages that Monica put together of Marco and then it came time for the cake. Monica was strictly no candles because it wasn't COVID safe so Marco sliced it up for everyone. I had to go around and apologise for the thickness of the sour cream frosting but it turns out everyone is a bit of a frosting addict too!

"Do I give you my doctor's details or do I give him yours?" said Marco eating his second slice of the cake.

So tell me Dear Reader, do you make sheet cakes often? Do you have a current flavour combo that you like? And what is your favourite frosting?

Chocolate Sheet Cake

Chocolate & Peanut Butter Sheet Cake

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An Original Recipe by Lorraine Elliott

Preparation time: 30 minutes

Cooking time: 1 hour 5 minutes

Serves: 20

The cake is best baked the day before

  • 1.5 cups/225g/8ozs. cake flour*
  • 1.5 cups/330g/11.6ozs. brown sugar, firmly packed
  • 50g/1.7ozs cocoa powder
  • 2 teaspoons bicarb
  • 1 teaspoon baking powder
  • 1 cup/250ml/8.8ozs. soda water
  • 1/2 cup/125ml/4flozs coffee
  • 1/2 cup/125ml/4flozs oil (mild flavoured)
  • 2 eggs, room temperature
  • 1 tablespoon vanilla bean paste
  • 100g/3.5ozs. dark chocolate, finely chopped
  • 100g/3.5ozs. Reese's peanut butter chips, finely chopped
  • 1 cup peanut butter (smooth or crunchy)

For Chocolate Sour Cream Frosting

  • 450g/1lb icing or powdered sugar
  • 20g/0.7oz cocoa powder

  • 90g/3ozs. dark chocolate chips, finely chopped

  • 90g/3ozs Reese's peanut butter chips, finely chopped
  • 90g/3ozs. butter
  • 2 teaspoons vanilla bean paste
  • Fat pinch salt
  • 180g/6ozs. full fat sour cream

To decorate

  • Cookie letters and sprinkles

Cake flour can be bought at the supermarket. You can also make it at home. To make 1 cup/150g/5.2ozs of cake flour replace 2 tablespoons of plain all purpose flour with cornflour/fine cornstarch and whisk well. I usually mix up a big batch of this and keep it in a container ready for baking cakes as it produces a softer texture.

Chocolate Sheet Cake

Step 1 - Preheat oven to 160C/320F and line a 30x20x5cm/12x8x2inch lamington pan on the base and sides with the sides going up a couple of inches. In a large bowl sift the cake flour, brown sugar, cocoa powder, bicarb and baking powder. In a jug measure the soda water, coffee, oil and whisk in the eggs and vanilla. Make a well in the centre of the dry ingredients and mix in the liquids gradually ensuring there are no lumps. Mix in the chocolate and pour into the prepared tin.

Thermomix directions for cake: note: you can also finely chop the chocolate in the Thermomix. I would do this first at speed #7 for 10 seconds (it will be noisy) and then place in a bowl until needed. Preheat oven to 160C/320F and line a 30x20x5cm/12x8x2inch lamington pan on the base and sides with the sides going up a couple of inches. Place the cake flour, brown sugar, cocoa powder, bicarb, baking powder and reserved chopped chocolate and set to speed #7 10 seconds. Add the soda water, coffee, oil, eggs, vanilla and set to 20 seconds on speed #5. Pour into the prepared tin.

Chocolate Sheet Cake

Step 2 -Dollop teaspoonfuls of peanut butter into the chocolate batter and then gently submerge these with your finger. Allow the cake batter to rest on the counter for 5 minutes and then bake in the centre of the oven for 45-50 minutes until the centre springs back when gently pressed. Cool the cake in the tin on a rack. The cake must be completely cold before icing or the icing will melt.

Chocolate Sheet Cake

Chocolate Sheet Cake

Step 3 - To make the frosting place the icing sugar and cocoa powder in a food processor and process until all lumps are removed. In a bowl melt the two types of chocolate with the butter in a double boiler or in the microwave on 50% power and stir until smooth. Place in the food processor with the icing sugar and cocoa. Add in vanilla, salt and sour cream and process until smooth. You can also do this by hand by mixing in the icing sugar but it's faster using the food processor or Thermomix (and I hate sifting!). Spread on top of cake and add sprinkles and letters if you want.

Chocolate Sheet Cake

Thermomix directions for frosting: place the icing sugar and cocoa powder in the Thermomix: 10 seconds, speed #9 until all lumps are removed. Place in a bowl. Then add the chocolate to the Thermomix and set to speed# 7 for 30 seconds. Add the butter and set to reverse, 50C for 5 minutes but halfway check that all of the chocolate is melting and not on the blade or sides. Insert butterfly attachment, add half of the sugar mixture and set to speed#4, 15 seconds. Add the vanilla, salt, sour cream and remaining sugar cocoa mixture and repeat on speed#4, 15 seconds

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