This Construction Cake will put the biggest smile on your little one’s face! Easy moist chocolate cake with less sweet vanilla buttercream

Happy 3rd birthday Kai!

Just as our plane takes off on our trip back to Sydney from New Zealand, I turn to my husband Tomi and announced ‘Let’s throw a big birthday party for Kai!’. Still exhausted from our trip, Tomi gazes at me with his bloodshot eyes. ‘Are you sure you want to do this?’ he asked reluctantly.

‘Yes! We have a month to plan, so it’s going to be a piece of cake!‘ I replied confidently.

We proactivity sent the invites immediately, but only to procrastinate. The RSVP came in, and approximately 50 guests (mostly adults) confirmed they would come. Cool, we still have another two weeks to kill this, we’re still good!

Then we found ourselves in the last week and panicked. I had envisioned how everything would turn out at Kai’s party but the end result was far from it!

We were sold an empty gas cylinder so we had no balloons! This was discovered an hour before our guests arrived, so we had to forgo the balloons.

There was just so much happening at one time, Tomi was trying (but failing) to fix our guest toilet and inflate the jumping castle. With all the drama unfolding, I wasn’t able to prepare all the dishes I wanted to serve.

Something inside me just went, ‘Oh well, it is what it is!’ I shrugged because nothing was going to stop me from having a good time. Kai had an amazing time and loved being in the middle of attention. I almost died from the cuteness overload when he unsuccessfully tried his hardest to blow out his birthday candle.

What’s in this Construction Cake?

Let’s just say I’m not a natural baker! I mean, I’m not terrible at baking but I have to try very hard! So if you’re not a confident baker, rest assured you can make this cake too!

I’m made 2 of Kai’s birthday cake so far. Last year was a Lion Cake with Mango & Cream, and this year it’s a Construction Cake. It had to be a Construction cake as Kai’s obsessed with working trucks and even knows how to clearly pronunce excavator!

We have a three-layer simple but delicious chocolate cake that stays moist for at least 3 days, even when chilled in the fridge. The buttercream is Ermine frosting, which is used to fill inbetween the layers and cover the entire cake.

What is Ermine frosting?

Ermine frosting is made from flour, milk, sugar, butter and vanilla extract. The flour, milk and sugar are heated together to make a roux. Once the roux has cooled down, it’s then whipped with softened butter.

What does Ermine frosting taste like?

You would probably expect the icing to taste floury, but it actually doesn’t. It tastes like a mix of Swiss buttercream and fresh whipped cream. Ermine frosting is also less sweet when compared to regular buttercream. It also has a lovely fluffy texture and is not grainy from the sugar.

How long can Ermine frosting sit at room temperature?

It’s spring here, and it was quite warm. The cake lasted an hour sitting out at room temperature. On a cool day, it should last 3 to 4 hours.

I have to admit that I almost threw my hands in the air and gave up constructing this construction cake!

This is not a complicated cake, but there are a few steps involved. Me being me; I got lazy and wanted to quit when the buttercream didn’t look perfect. Luckily, some common sense prevailed, and I pushed all the way through. Anyway, why does a 3-year-old cake need to look perfect?!

If you don’t have the time to bake a construction cake or have $200 to buy one, just cheat a little!

Grab some store-bought vanilla or chocolate round sponge cake and, if you like, some already to go cake frosting as well. However, I recommend making the buttercream as it’ll taste much better than the store-bought ones. This way, you’ll just have to focus on decorating the cake.

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Ingredients for Construction Cake

I forgot to take a photo of the optional decorations because my kitchen was a disaster at that stage!

Plain flour (all-purpose flour) does not have any leavening or raising agents (such as baking powder) mixed into the flour.

Caster sugar (superfine sugar) – Caster sugar has finer granules than regular white sugar, but it’s not the same as icing/powdered sugar. Many baking or candy recipes call for caster sugar as it dissolves faster and better into mixtures. If you can’t find caster sugar, you can make your own by placing regular sugar in a food processor or blender. Pulse the sugar a few times until it looks finer, but don’t over-blitz to a powder consistency. However, you could just use equal amounts of regular white sugar.

Fondant or icing – To make life easier, I bought ready-to-roll fondant/icing from the supermarket. It came in a hard rectangle block wrapped in plastic. All I needed to do was roll it out and cut it into shapes. Mine was orange and black, but you could use any two colours.

Construction truck toys – I found a packet of these cute construction trucks in the toys area at my local BIG W (discounted department store). The traffic cones (witches’ hats) are candles, which I found there as well.

Food colouring – I used gel food colouring as only a few drops will give us a deep or vibrant colour. Mine was black and yellow, but you could use whatever colours you like for the outer layer of the buttercream.

How to make a Construction Cake

Step-by-step guide with photos

For the chocolate cake:

Preheat oven to 180°C (360°F) or 160°C (320°F) for fan-forced ovens. Grease and line the sides and bases of 3 x 20cm (8in) round cake tins with non-stick baking/parchment paper.

Sift the flour, cocoa powder, sugar, baking soda, baking powder and salt into a large bowl, then give it a whisk to combine. Make a well in the centre of the dry ingredients, then add in the oil, milk, eggs and vanilla extract. Whisk to combine until smooth, then add in the boiled water, and continue to whisk for 10 -15 seconds. The batter should be very runny.

Pour the batter evenly into the prepared tins. Bake for 30 to 35 minutes or until a skewer comes out clean when inserted into the centre of each cake.

Leave the cakes to cool in their tins for 15 minutes, then turn them out onto a cooling rack. Allow the cakes to cool completely before frosting them.

For the roux and Ermine frosting:

Whilst waiting for the cake to bake, make the roux. Place sugar and flour into a large saucepan and place it over medium heat, then stir for 30 seconds. Slowly drizzle in the milk whilst whisking constantly so the mixture won’t catch to the bottom of the pan. The roux will slowly thicken, continue to cook and stir until it’s thick like custard.

Transfer the roux into a bowl, then cover it with plastic film. Press the film down so it clings onto the surface of the roux so a skin doesn’t form. Allow the roux to cool completely at room temperature.

Using a hand or stand mixer, beat the butter at low speed for 10 seconds with the whisk attachment. Increase the speed to high and beat the butter for 5 minutes or until it looks very pale. Scape the sides and bottom of the bowl with a spatula and whisk again for 20 seconds. Add in the vanilla and salt and beat for another 20 seconds. With the mixer still running and at high speed, place in the cooled roux mixture a spoonful at a time. Beat until the buttercream is thick, fluffy and can hold its shape.

Filling and crumb coat:

Use a cake leveller to slice each cake evenly or carefully use a long bread knife to slice the tops off to make them flat. Place a cake on a cake board on top of the cake turntable. For the filling, use a small cake scoop (approx. 1.5 tbsp) and place 4 scoops of frosting over the cake, then use a spatula to spread the icing. Repeat with the second cake layer and filling.

For the crumb coating top of the cake with 4 scoops of frosting, use a long flat spatula to spread the buttercream thinly on the top and sides of the cake. Chill the cake in the fridge for a minimum of 1 hour or 20 minutes in the freezer.

Decorating and finishing:

Place another layer of frosting over the top of the cake and only halfway down the side of the cake, and level it out using a long spatula. Divide the remaining frosting evenly into two bowls. Place 1 or 2 drops of yellow food colouring in one and black in the other. Mix well until the colour looks even. Use a spatula to spread the yellow frosting on the side of the cake in the middle, then spread the bottom section of the cake with the grey frosting. Spin the turntable and even out the frosting with a spatula.

Use a rolling pin to roll the coloured fondant/icing until it’s thin but won’t tear when you lift it. Cut the orange fondant into a banner shape of your choice. Use a letter cutter to write your little one’s name with the black fondant, then lightly press the letters onto the banner. If the letters don’t stick, brush a little water on the back of the letters. Carefully stick the banner on the side of the cake.

Place the Oreos into a food processor and blitz them into crumbs. This will be the dirt, place it anywhere you like around and on top of the cake. Place the construction toys on top and on the bottom of the cake. Place some Maltesers in the dirt.

Leftovers – Transfer the cake into a covered cake container and store it in the fridge for up to 3 to 4 days.

I’ve used a third-party application to calculate the calories and nutritional information, so please use this as an approximate guide only.

Cooking measurements are in Australian standard spoon and cup measurements. For specific details and conversions, visit our Australian Cooking Measurements page.

I would love your feedback and support if you made this recipe. To do this, please rate this recipe and provide a comment by scrolling down this page or by clicking that green circle on the bottom left. An email address is required (for spam), but it won’t be published. I would also love to see your dish, so don’t forget to tag me on my Instagram account ‘3catsfoodie’

Cheers – Cat T