Old School Chocolate Traybake Cake

Published: Jun 15, 2024 · Modified: Aug 6, 2024 by Chloe · This post may contain affiliate links · 57 Comments

This old school chocolate traybake cake is so simple but super delicious! It's a soft, fluffy chocolate sheet cake topped with simple chocolate glace icing and chocolate sprinkles.

squares of old school chocolate traybake cake with icing and sprinkles on top

I'm back with another old-school cake recipe, this time it's a chocolate one! I recently posted my vanilla school dinner cake recipe as well as my jam and coconut sponge cake, and my Cornflake tart traybake has proved to be a hit so far. So naturally, chocolate cake traybake just had to come next!

This cake is super easy to make and uses less than 10 simple ingredients so it's great for kids to help with. It's perfect for a simple birthday cake, a bake sale treat, or an after-dinner dessert. It's even more amazing served with warm custard, which is how they used to serve it at my school in the 90s. I can't wait for you to try it!

For the readers who are new to cake baking, I've written out detailed notes, tips and step-by-step images with photos in the post below. I hope this will help you get success on the first try. And for the more experienced bakers, there's a short, condensed version of the recipe in the card at the end of the post. Enjoy!

old school dinner chocolate traybake slices on a white surface

Ingredient notes

Butter: Use unsalted butter for this cake- you can add a pinch of salt separately to the cake mix if you like but I personally don't. Make sure to soften the butter before baking by letting it sit out at room temperature for 60 minutes.
Caster sugar: Caster sugar is a finer version of granulated white sugar and helps to improve the texture of baked goods. It's also known as superfine sugar in the USA.
Eggs: Eggs bind the rest of the ingredients together and help with leavening. You'll need 4 medium eggs for this cake.
Vanilla extract: To add extra flavour. If you want to really enhance the chocolate flavour, you can swap this out for a teaspoon of cold espresso. You won't taste the coffee at all but the chocolate flavour will be more intense.
Self-raising flour: Self-raising flour is the best type to use for this cake to get the perfect fluffy texture. If plain/all-purpose flour is all you have, you can use it as a 1:1 substitute alonge with 2 teaspoons of baking powder.
Milk: 3 tablespoons to help loosen the cake mix.
Cocoa powder: For the chocolate flavour. We'll use this both in the cake mix and in the glace icing.
Icing sugar: Mixed with cocoa powder and a small amount of milk, this will create a thick, glossy icing that goes perfectly with old school chocolate traybake cake.
Chocolate sprinkles: The finishing touch! I used chocolate strands but feel free to use whichever ones you like best.

Equipment/tools

Kitchen scales: When it comes to baking, accuracy is important. I recommend using grams to measure, which is why I usually don't include imperial measurements in my recipes.
8x10-inch tin: This is the size of tin I always use for my cakes so use this if you can. It will help you get a nice, thick, fluffy cake.
Baking paper: To stop the cake from getting stuck. You can leave a bit hanging over each edge so you can just lift the cake out later.
Electric hand whisk: I recommend using an electric hand whisk or stand mixer to make the cake batter. It can be done by hand but it takes quite a bit more effort.
Bowls and utensils: You'll need a large bowl for mixing the batter and a smaller one for the icing, as well as a wooden spoon or spatula, a tablespoon, a teaspoon and a sharp knife.

close up of old school chocolate traybake slice

How to make old school chocolate cake traybake

Step 1: Preheat your oven to 180°C (or 160°C if you're using a fan oven). Line an 8x10-inch tin with baking paper.

Step 2: In a large bowl, whisk together 250g softened butter and 250g caster sugar until soft and fluffy. Then stir in 1 teaspoon of vanilla extract.

butter and sugar creamed together in a bowl

Step 3: Measure out 220g of self-raising flour and 30g of cocoa powder. Mix it into the butter/sugar mixture along with 4 eggs and 3 tablespoons of milk. Mix them in a little bit at a time to prevent curdling.

Step 4: Transfer the cake batter to your lined tin and bake for 25-30 minutes, or until a toothpick through the middle comes out clean. Let the cake cool for about 10 minutes then gently flip it out onto a wire rack. Leave to cool completely.

Step 5: Prepare your chocolate glace icing by mixing together 190g of icing sugar, 1 tablespoon of cocoa powder and 2 tablespoons of milk. If you want thicker icing, add more icing sugar. If you want it thinner, add more milk or water.

Step 6: Spread the icing evenly over your cooled cake and top with a few tablespoons of chocolate sprinkles. Let the cake sit at room temperature until the icing has hardened, then cut it into slices and enjoy!

spreading chocolate icing onto sheet cake

Top tips

8x10-inch is the best size of tin to use for a thick cake. I highly recommend it!
If you don't have chocolate sprinkles to hand, you can use a vegetable peeler to create decorative curls from your favourite bar of chocolate.
For a more decadent dessert, top your chocolate traybake with buttercream instead of glace icing.

FAQ

How long does old school chocolate cake last?

This cake will last for up to 5 days so long as you keep it in an airtight container. I like to store it in the kitchen cupboard but it can also be kept in the fridge if you want.

Can I freeze this recipe?

Yes. Pop your cake slices into airtight containers and freeze for up to 3 months. To defrost it, just let it sit out at room temperature on a wire rack or plate for 1-2 hours.

Can I use a 9x12-inch tin?

Yes, you can use a slightly larger tin but be aware that the cake will turn out a little bit thinner. The baking time will also differ so make sure to keep an eye on it while it's in the oven. You can use my cake pan converter for other tin sizes.

Can this cake be made gluten-free?

Yes, you can make this recipe gluten-free by swapping the self-raising flour for a gluten-free self-raising flour blend. If your blend doesn't already contain xanthan gum, make sure to add ¼ teaspoon of it separately to prevent the cake from crumbling.

hand holding up a slice of chocolate traybake cake

More traybake recipes:

I hope you like this old school chocolate cake traybake recipe. If you try it at home, please leave a comment and rating below to let me know what you think. Enjoy!