Go Back
Kid's Construction Party

Kid's Chocolate Construction Site Cake

A favourite chocolate cake that appeals to kids and adults alike. The cake is cut out to look like a quarry with construction vehicle toys placed on top - this is an easy cake to decorate for your child’s next birthday party!

Prep Time 1 hour 30 minutes
Cook Time 40 minutes
Total Time 2 hours 10 minutes
Servings 20 +
Author My Little Larder


For the cake:

  • 2 2/3 cup all-purpose flour
  • 1 1/4 cup + 3 Tbsp unsweetened cocoa powder
  • 2 tsp baking powder
  • 1 tsp baking soda
  • 1 tsp sea salt
  • 1 cup sour cream
  • 1 tsp vanilla extract
  • 1 tsp almond extract
  • 1 cup unsalted butter, softened
  • 2 cups caster sugar
  • 2 large free-range eggs
  • 1 1/4 cups strong coffee, cold (I use decaf for children)

For the ganache filling:

  • 200 g/7oz dark chocolate (at least 50 percent solids, but I prefer 70 percent, chopped)
  • 2/3 cup cream liquid

For the chocolate Swiss meringue buttercream:

  • 1 1/4 cups caster sugar
  • 5 large free-range egg whites
  • 340 g/ 3 sticks unsalted butter, room temperature and chopped into roughly 1cm/1/2in cubes
  • 255 g/9oz chocolate (at least 50 percent solids, but I prefer 70 percent, melted and cooled)

To serve:

  • handful Momofuku milk bar chocolate crumbs (link for recipe in instructions below)
  • a few handfuls of chocolate coated raisins, to look like boulders, chocolate coated honeycomb (to look like boulders), Maltesers (to look like boulders), chocolate finger biscuits (to look like logs), and mini-construction vehicle toys


For the cake:

  1. Preheat oven to 180C/350F on bake. Grease and line 2 x 20cm/8in round cake tins.

  2. In a large bowl, sift or whisk together flour, cocoa powder, baking powder, baking soda and salt. Set aside.

  3. In a small bowl, mix together sour cream, vanilla extract and almond extract. Set aside.

  4. In the bowl of a standing mixer fitted with a paddle attachment cream together butter and sugar on medium high speed until pale and fluffy. Add eggs one at a time ensuring that each one is fully incorporated after each addition. If the mixture looks like it has curdled or split, add a tablespoon of flour mixture.

  5. Add 1/3 flour mixture and mix until incorporated. Add 1/2 sour cream mixture and mix, followed by 1/3 flour mixture, remaining sour cream then last 1/3 flour mixture.

  6. Gradually pour in coffee and mix until combined.

  7. Divide batter between two tins and place in oven for 40 min or until a skewer comes out clean when inserted into the centre of the cake.

  8. Allow cakes to cool for 10 min in their tins before turning out and allowing to cool fully on a wire rack.

For the ganache filling:

  1. Place chocolate in a heat proof bowl. Heat cream in a small saucepan over medium heat until bubbles are forming around the edge of the cream.

  2. Pour cream over chocolate and allow to stand for 5 minutes.

  3. Stir until fully mixed, glossy and smooth.

  4. Allow to stand at room temperature (or in the fridge for hot climates) until the mixture has thickened and is of a spreadable consistency.

For the frosting:

  1. Place a heatproof bowl over a saucepan of simmering water. Add sugar and egg whites to the bowl.

  2. Whisk until sugar has dissolved and temperature reaches 60C/140F on a candy thermometer. This ensures that the eggs have been pasteurised making them safe for children and pregnant women to eat.

  3. Transfer egg and sugar mixture the bowl of a standing electric mixer fitted with a whisk attachment. Whisk on high until the mixture is cool (feel the bottom of the bowl with your hand to check), about 7-10 min.

  4. Change to a paddle attachment and reduce speed to medium-high. Slowly add butter a few cubes at a time. It helps to remember that you are trying to create an emulsion here (like making mayonnaise) so you don’t want to add the butter too fast. Continue adding until all the butter has been incorporated. Be aware that at some point near the end of adding the butter the mixture will look quite strange, almost curd-like, then it will magically turn to a smooth, pillowy buttercream consistency. If yours looks like scrambled egg (mine has done this many times) see notes for troubleshooting.

  5. Gradually add cooled chocolate until fully incorporated.

To assemble:

  1. Level cake if necessary by cutting off the domed tops. Halve each cake horizontally using a serrated knife or cake leveller.

  2. Reserve 2 Tbsp ganache mixture. Place a cake half on a cake stand or cake board and top with 1/3 ganache mixture. Top with next cake half and 1/3 ganache mixture, followed by another cake half, remaining ganache then top with final cake layer. Place in the refrigerator for 15 min if required to firm up the cake.

  3. Using a small serrated knife or paring knife, cut out a big chunk of the cake to make it look like a quarry. You can be as messy as you like with this because we will be covering it up with frosting. Smear 2 Tbsp ganache on top of cake then place the piece of cake you just cut out upside down to the ganache to look like a hill on top of the cake.

  4. Cover the entire cake in a thin layer of frosting. It doesn’t matter if you get crumbs in it, you most likely will, because we will be covering it will another layer of frosting. Refrigerate for 15 min to firm up.

  5. Cover the entire cake in remaining frosting, you can be a little messy if you like to make it look like dirt and rocks.

  6. Sprinkle chocolate crumbs around the cake to look like dirt. Place construction vehicles around the cake then sprinkle over chocolate raisins, honeycomb, fingers and Maltesers to look like boulders.

  7. Cake is best eaten on the day but unfrosted cakes will keep overnight in an airtight container and frosted cake will keep up to 3 days. I made this cake the day before and it was delicious and fresh on the day.

Recipe Notes

If your SWB looks like scrambled egg then it has curdled most likely because your butter was too cold when you added it or it was added too quickly and you don't have a successful emulsion. The best thing to do at this point is to take approximately 1/4 of your mixture and transfer it to a microwave proof bowl. Microwave for a few seconds until it is the consistency of creamy soup. Add it slowly back to your original mixture beating as you go, the mixture should then emulsify and you will have smooth pillowy buttercream. For great troubleshooting visit The Polkadotter.