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Chocolate Sheet Cake

by Nigella

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Introduction

I love an American sheet cake — it’s a great way to feed a lot of people and, in my book, the more people get to eat cake, the better. I’ve simplified what is an already simple approach, so that both cake, and icing/frosting are made in saucepans on the stovetop: in other words, no creaming and multi-stepped process, just melting, stirring and pouring. It’s also easily transportable, making it great — in particular — for bake sales, but also to be borne in mind when you want to go armed to a friend’s house with something sweet.

Add any decoration you like to this crackle-glazed, fudgy cake. I’ve used white chocolate stars here, but consider hundreds and thousands, chocolate vermicelli, any manner of sprinkles or even an exotic scattering of pistachios and rose petals.

For US cup measures, use the toggle at the top of the ingredients list.

Ingredients

Yields: 12 big squares, 24 bars or 48 after-dinner bites

Metric Cups

For the Cake

125 millilitres full fat milk or semi-skimmed / 2% milk
2 teaspoons white wine vinegar or cider vinegar
200 grams soft unsalted butter
20 grams best-quality cocoa powder
200 grams caster sugar
1 teaspoon bicarbonate of soda
1 pinch of salt
300 grams plain flour
2 large eggs
1 teaspoon vanilla extract

For the Icing/Frosting

50 grams soft unsalted butter
3 tablespoons full fat milk or semi-skimmed / 2% milk
2 tablespoons best-quality cocoa powder
150 grams icing sugar (sieved)
1 teaspoon vanilla extract

To Decorate

sprinkles of your choice

For the Cake

½ cup whole milk or semi-skimmed / 2% milk
2 teaspoons white wine vinegar or cider vinegar
1 cup soft unsalted butter
¼ cup best-quality unsweetened cocoa
1 cup superfine sugar
1 teaspoon baking soda
1 pinch of salt
2 cups all-purpose flour
2 large eggs
1 teaspoon vanilla extract

For the Icing/Frosting

¼ cup soft unsalted butter
3 tablespoons whole milk or semi-skimmed / 2% milk
2 tablespoons best-quality unsweetened cocoa
1½ cups confectioners' sugar (sieved)
1 teaspoon vanilla extract

To Decorate

sprinkles of your choice

Method

Preheat the oven to 180ºC/160ºC Fan/350ºF and grease and line a shallow 33cm x 23cm / 13 x 9 inch roasting tin. A 30cm x 20cm / 12 x 8 inch one would also do. Measure out the milk in a jug big enough to take the eggs later as well, and add the vinegar. Stir and leave while you get on with the rest of the cake.
Into a heavy-based saucepan (large enough to take the rest of the cake ingredients later), pour 250m/1 cup of water, then spoon or slice in the butter, and add the cocoa and put over a medium heat — stirring occasionally with a wooden spoon until the butter melts and the cocoa dissolves. Remove from the heat.
Measure the sugar, bicarb, salt and flour into a bowl, and fork to mix.
Add the eggs and vanilla to the ‘buttermilk’ in its jug and whisk well to combine. The eggs should be fully incorporated.
Now, add the dry ingredients to the slightly cooled pan, beating well with a wooden spoon or a little whisk, followed by the jugful of wet ingredients. Keep on beating until everything is smoothly combined and pour into the prepared tin and place on a middle rack in the preheated oven.
Measure out everything you need for the frosting/icing, but do not mix together until the cake is just out of the oven as the icing sets quickly and the cake needs to be iced while it’s still hot. Make sure your decorations are to hand, too.
The cake needs 20 minutes but it’s always wise to start testing earlier, as ovens do vary. When a cake tester comes out clean, it’s cooked. Sit tin on a wire rack.
To make the icing, melt the butter, milk and cocoa in a medium-sized saucepan over a low to medium heat, keep stirring with a small whisk and do not let boil.
Once everything is melted and smooth, take the pan off the heat and whisk in the icing sugar and vanilla. Keep whisking till all is glossily amalgamated, and a good consistency to cover the cake. Immediately, pour over the waiting cake, spreading it out with a little spatula as you need. Without further ado, add whatever decorations you desire and leave in tin to cool before cutting into shallow squares.

Preheat the oven to 180ºC/160ºC Fan/350ºF and grease and line a shallow 33cm x 23cm / 13 x 9 inch roasting tin. A 30cm x 20cm / 12 x 8 inch one would also do. Measure out the milk in a jug big enough to take the eggs later as well, and add the vinegar. Stir and leave while you get on with the rest of the cake.
Into a heavy-based saucepan (large enough to take the rest of the cake ingredients later), pour 250m/1 cup of water, then spoon or slice in the butter, and add the cocoa and put over a medium heat — stirring occasionally with a wooden spoon until the butter melts and the cocoa dissolves. Remove from the heat.
Measure the sugar, bicarb, salt and flour into a bowl, and fork to mix.
Add the eggs and vanilla to the ‘buttermilk’ in its jug and whisk well to combine. The eggs should be fully incorporated.
Now, add the dry ingredients to the slightly cooled pan, beating well with a wooden spoon or a little whisk, followed by the jugful of wet ingredients. Keep on beating until everything is smoothly combined and pour into the prepared tin and place on a middle rack in the preheated oven.
Measure out everything you need for the frosting/icing, but do not mix together until the cake is just out of the oven as the icing sets quickly and the cake needs to be iced while it’s still hot. Make sure your decorations are to hand, too.
The cake needs 20 minutes but it’s always wise to start testing earlier, as ovens do vary. When a cake tester comes out clean, it’s cooked. Sit tin on a wire rack.
To make the icing, melt the butter, milk and cocoa in a medium-sized saucepan over a low to medium heat, keep stirring with a small whisk and do not let boil.
Once everything is melted and smooth, take the pan off the heat and whisk in the confectioners' sugar and vanilla. Keep whisking till all is glossily amalgamated, and a good consistency to cover the cake. Immediately, pour over the waiting cake, spreading it out with a little spatula as you need. Without further ado, add whatever decorations you desire and leave in tin to cool before cutting into shallow squares.

Additional Information

MAKE AHEAD / STORE:
Store in an airtight container in a cool place for up to 5 days. Leftovers can be frozen in an airtight container for up to 3 months but note that the fudgy icing can become slightly sticky when defrosted. Thaw at room temperature for 2-3 hours.

Tell us what you think

What 20 Others have said

My Auntie made this cake for every family picnic. She called it Wacky cake and added walnuts to the frosting. Divine.

Posted by Gamiato3 on 13th June 2018
Easy to make and hopefully good to eat! Tell you next time.

Posted by Mamia on 10th August 2016
Made this yesterday, it's been found to be very addictive in this household and we've not got much left, definitely one to make again.

Posted by Josiejo72 on 17th April 2016
This cake is so good. Go and make it right now.

Posted by fionagirl on 3rd January 2016
Made this & loved it! As I adore buttermilk cakes (& pancakes) however do not always have some in the fridge,it was great to learn that adding vinegar to milk equals hey presto buttermilk without leaving the house! Want to experiment & make a coffee sheet cake next. So good to see you back on tv Nigella plus reignited my love for kitchen aid mixers that has been burgeoning for many years...surrendered to it now & we've ordered one :)

Posted by Babels on 28th December 2015
It sounds very delicious, although the use of the term icing sugar threw me for a loop, I had to look that term up, I had heard it referred to as confectioners and powdered sugar, but now I can add a new term to my book.

Posted by BakerCait on 13th August 2015
thank you Nigella for this awsome recipe!

Posted by Katerinaki on 27th April 2015
This recipe was so cool, easy to follow and give amazing results. It was my first ever cake and came out amazing.

Posted by Rbmkhtr on 20th February 2015
I always love ur recipes...I tried it yesterday and it was awesome...thanx for sharing it with us.

Posted by shivanigupta3 on 29th October 2014
i will surely try this cake out as all the recipes i have tried so far have been very successful (if i may say so) of Nigella's. Thanks for being such a wonderful cook. You truly are a domestic godess. I have 4 of your cook books and tried out most of the recipes. Though some ingredients are not available in india , I have subtituted and have come out well.

Posted by yardley pal on 21st October 2014
So easy, looks good, yet to taste. BUT don't use chocolate decorations such as curls as they start to melt as the icing is still rather warm!

Posted by Jofruitbat on 12th October 2014
Easy to make and even easier to eat. Making another one for Macmillan coffee morning tomorrow.

Posted by Tamzingarrod on 25th September 2014