Galaxy cake

Step into another world with this galaxy themed, fudgy chocolate, salted caramel and Mars bar cake. The perfect bake for stargazers and children alike!

  • Prep:2 hrs
    Cook:45 mins
    plus chilling
  • Serves 20
  • A challenge

Nutrition per serving

  • kcal 719
  • fat 38g
  • saturates 23g
  • carbs 87g
  • sugars 78g
  • fibre 2g
  • protein 5g
  • salt 0.8g


  • 250g unsalted butter
  • 200g dark chocolate (70% cocoa solids)
  • 350g light soft brown sugar
  • 200g self-raising flour
  • 1 tsp bicarbonate of soda?
  • ½ tsp salt
  • 4 large eggs
  • 300ml tub sour cream
  • 100ml strong hot coffee (double shot of espresso)
  • 250g fun size bag of mini Mars Bars
  • 397g can Nestlé Carnation Caramel
  • 1 tsp flaky sea salt
  • 400g unsalted butter, softened at room temperature
  • 800g icing sugar
  • 2 tsp vanilla bean paste
  • 4 tbsp whole milk
  • black, blue, purple and green food colouring gel
  • navy and silver lustre dust
  • edible metallic pearlescent white paint
  • silver pearl balls
  • thin paintbrush
  • cake scraper


Freezing the cakes

You can bake the sponges in advance and freeze them, well covered, and can even decorate them from frozen as this will make it easier to work with the buttercream.

Where to buy

We bought all the edible decoration ingredients from Amazon. 


Please feel free to change the decorations as you see fit, use different colours, however you want. When creating a galaxy the possibilities are infinite.



  1. Heat the oven to 180c/160 fan/gas mark 4. Grease and bottom line two deep 20cm spring form cake tins. Using the microwave on high, melt the butter with the chocolate in 30 second bursts until glossy and smooth. Alternatively melt in a bowl over a pan of simmering water. Leave to cool slightly.

  2. Combine the sugar and flour in a large bowl, getting rid of any lumps with your fingertips, then stir in the bicarb and salt. In a separate jug beat the eggs with the sour cream then pour into the dry ingredients and whisk until well combined. Scrape in the cooled chocolate mixture and beat until you have a smooth chocolatey batter. Stir in the hot coffee then divide the mixture between the tins and bake for 40-45mins until a skewer inserted in the centre comes out clean. Leave to cool in the tins for 10 mins then transfer to a wire rack to cool completely.

  3. While the cakes are cooling make the buttercream. Using a food mixer or an electric whisk beat the butter with the icing sugar, vanilla and a pinch of salt for 10 mins until very light and fluffy, then whisk in the milk. Set aside.

  4. Slice each of the cooled cakes into two. Break the Mars bars into small pieces and stir the sea salt through the caramel. Sandwich the cakes together using a 1/3 of the caramel and Mars between each layer, leaving the top layer free for icing.

  5. Crumb coat the cake completely in a layer of white buttercream then pop in the fridge to set. Meanwhile divide the remaining butter cream between 4 bowls, and colour each with the black, blue, green and purple food colouring.

  6. Using a palette knife dot the cake at random with a little of each coloured buttercream then using the cake scraper go around the sides to blend the colours together and smooth the cake. Keep layering different colours of buttercream until you have your desired galaxy appearance.

  7. Dot areas with the navy and silver lustre dust so that you create a moon beam effect around the cake. Using the paintbrush and white pearlescent paint, draw clusters of stars and dot in silver balls, being as random or as coordinated as you and your galaxy like.

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