Michelle Darmody: How to bake a classic chocolate sheet cake — and the mistakes to avoid

With a sheet cake, you have the bonus of a large canvas which can be drawn on, or decorated, for a celebration event.

Sheet cakes or tray bakes — whichever words you want to use — are very handy for occasions when you need to cater for large groups. 

Baking a cake in one solid rectangle makes it much easier for slicing and storing than a taller, circular cake. 

With a sheet cake, you have the bonus of a large canvas which can be drawn on, or decorated, for a celebration event. 

If elaborate decorating is not your forte you can cut the cake into squares and pile them into a pyramid and top with candles. 

It is already sliced and ready to eat once the candles are blown.

One thing to be aware of is that the wider and flatter a cake is, the more prone it is to drying out as it bakes, so having a very moist batter to begin with does help. 

This recipe is much lighter than a brownie and less challenging than a fancier cake. 

The chocolate ganache topping is a great thing to have in your repertoire and can be used in anything from making chocolate truffles to icing buns or filling tarts. 

Here, it adds a smooth, rich layer and a glossy covering for this versatile and popular cake.

Chocolate Sheet Cake

recipe by:Michelle Darmody

With a sheet cake, you have the bonus of a large canvas which can be drawn on, or decorated, for a celebration event.

Servings

12

Preparation Time

 25 mins

Cooking Time

 40 mins

Total Time

 1 hours 5 mins

Course

 Baking

Ingredients

• For the cake:

• 300g soft butter

• 270g golden caster sugar

• 260g light muscovado sugar

• 360ml water

• 35g cocoa powder

• 370g self-raising flour

• 1 tsp of baking powder

• 185g crème fraîche

• 3 eggs, lightly beaten

• 1 tsp vanilla extract

• For the icing:

• 190ml of cream

• 200g of dark chocolate, broken into small even pieces

• 10g of soft butter

Method

1. Preheat your oven to 180ºC/gas mark 4 and line a 12 by 8-inch rectangular tin.

2. Place the butter, sugar and water into a saucepan and heat gently until the sugar has melted.

3. Sieve the cocoa powder, flour and baking together into a large bowl and make a well in the centre.

4. Pour the contents of the saucepan into the well in the flour. Add the crème fraîche, eggs and vanilla.

5. Stir until everything is well combined.

6. Scoop the mixture into the prepared tin and smooth it out.

7. Bake for about 40 minutes until a skewer comes out clean.

8. Allow to cool completely in the tin.

9. To make the icing, heat the cream until it is shivering, then stir in the chocolate and butter until they are both melted.

10. Allow to cool completely and then spread on the top of the cake.

Baker's tips

• Getting to know your oven can be vital for good baking results. For a flatter cake, like this, it is even more important, as having your oven turned up too high will dry out the cake. In my experience, all ovens are different and the temperature you read on the dial may not be accurate. You can get another oven thermometer and keep a strict eye, or you can take a mental note as you use your oven and adjust a little in either direction when you get to know what its true temperature is.
• Always aim to have your cake in the centre of your oven so there is good airflow all around it and it bakes evenly.
• Make sure to leave some parchment paper around the edges that can be used to remove the cake from the tin after baking. You can then gently pull on the parchment paper to lift out the cake. Peel back the paper before slicing. It is best to wait until it has cooled down completely before cutting.
• It is best not to let your batter sit for too long before baking as the raising agents in the flour and baking powder may start to diminish.
• If you are using a bar of chocolate rather than chocolate chips for the ganache it is best to break it as evenly as you can, so you do not have very large pieces that take a long time to melt while other little shards are getting burnt.
• This cake will not benefit from being kept in the fridge. The cold, relatively low-humidity environment will dry out the cake and make it stale ahead of time. Store in an airtight container in a cool place.
• Slices can be frozen in an airtight container for up to three months. It is best to freeze before icing. Thaw at room temperature for about three hours, then ice before serving.

Three delicious variations

Coffee buttercream sheet cake

Coffee and chocolate are a match made in heaven and the pairing of the two here makes for an elegant cake that can be divided easily. 

In place of the 360ml of water, use 320ml of water and 40mls of strong espresso. 

To ice the cake, whisk 110g of soft butter with 220g icing sugar and some very strong espresso which makes up about 10ml of liquid.

Whisk until completely light and fluffy.

Hazelnut chocolate sheet cake

There is a reason that chocolate hazelnut spread is loved the world over. 

The earthy, slightly sweet flavour of crushed hazelnuts works wonderfully with the smoothness of chocolate. 

To make this version, finely chop 150g of roasted hazelnuts and add them to the cake batter. 

Make the icing as instructed in the main recipe and sprinkle the top with another 20g of chopped roasted hazelnuts.

Raspberry chocolate sheet cake

The simple addition of a handful of fresh raspberries works wonders in the recipe. 

Roughly chop any very large berries and stir them in before you scoop the batter into your tin.