Galaxy Fault Line Cake

A galaxy fault line cake with an easy to make buttercream galaxy.


  • Cake
  • 630g (3 ¼ cups) plain (all-purpose) flour
  • 390g (1 ¾ cups) granulated sugar
  • 4.5 tsp baking powder
  • 1/2 tsp fine salt
  • 190g (¾ cups) unsalted butter, softened
  • 3 large eggs
  • 562ml (2 ¼ cups) full-cream (whole) milk
  • 190ml (¾ cup) vegetable oil
  • 3 tbsp Greek yoghurt (or sour cream)
  • 1 ½ tsp vanilla extract or vanilla bean paste
  • 1 tsp lemon flavouring
  • 10 drops teal food gel
  • Frosting
  • 2 batches swiss meringue buttercream frosting
  • Purple frosting: 5 drops purple food gel + 5 drops pink food gel
  • Mint frosting: 5 drops teal food gel
  • Black frosting: 2 tbsp cocoa powder + 10 drops black food gel
  • Dark purple frosting: 5 drops purple food gel + 5 drops black food gel
  • Dark Green frosting: 5 drops teal food gel + 5 drops black food gel
  • Pink frosting: 5 drops pink food gel
  • Blue frosting: 5 drops blue food gel
  • Decorations
  • ½ cup white caviar sprinkles


  1. Frosting
  2. To prepare your purple frosting add the purple food gel to ½ batch of frosting and use an electric hand mixer to mix until well combined and evenly coloured. You’ll colour all of your frosting in a similar way.
  3. To make the mint coloured frosting you’ll need another ½ batch of frosting.
  4. Split the remaining frosting into 5 bowls and use the colour combinations listed in the ingredients list to make up the rest of the colours.
  5. Cake
  6. Preheat a fan-forced oven to 140C (280F) or 160C (320F) for a conventional oven. Spray three 7” cake tins with oil spray and line the bottom with baking paper. Set aside
  7. Add the flour, sugar, baking powder and salt to a large mixing bowl and mix together using a hand mixer until well combined.
  8. Next add the softened butter and mix on low speed until mixture reaches a crumbly sand like texture.
  9. Add the eggs, milk, lemon flavouring, oil, Greek yogurt and vanilla extract. Mix on low speed until no dry ingredients are showing. Scrape down the bowl and mix for another 20 seconds. Add 3 drops teal food gel and mix until evenly coloured.
  10. Split the batter into two bowls. Set the light-coloured batter aside and add 7 drops of extra food gel into one half of the batter and mix it in.
  11. Add the two batters into two separate piping bags and snip a small piece of the end off. Drizzle squiggles of each batter into the three
  12. Fill three 8” cake tins with batter. I find using an ice cream scoop to help me do this makes it easy to distribute the batter evenly so that everything bakes at the same time.
  13. Bake for 50-60 min or until a toothpick inserted comes out clean. If the pick comes out with wet batter, bake for a further 10 min at a time until fully baked. Allow the cakes to cool to room temperature inside the cake tins and then chill them in the fridge overnight. Chilling your cakes overnight makes them easier to trim and decorate. So I bake my cakes the day before I decorate them.
  14. To trim your chilled cakes, use a cake leveller or large serrated knife to carefully trim the crust off the top of each cake. You’ll end up with 3 layers of cake.
  15. To crumb coat your cake, add a dab of purple frosting onto an 8” cake board or flat serving plate. Use a small offset spatula to spread the frosting around before adding the first cake layer. Gently press down the centre of the cake layer to make sure it’s stuck to the frosting underneath.
  16. Add frosting to a piping bag and frost a ring around the top of the cake. Fill the centre with more frosting. Use your small offset spatula to smoothen out the frosting before you add the next layer of cake. Repeat with the remaining layers.
  17. Add more frosting around and top and sides of the cake. Use the small spatula to smoothen out the top and sides of the cake, taking care to fill in any gaps in between each layer of cake.
  18. Use a cake scraper (otherwise known as a bench scraper) to smoothen out the frosting on the sides and top. Get it as neat as you can. This should just be a neat, thin layer of frosting which is aimed at trapping any cake crumbs so that random bits of cake crumbs don’t show up on the final layer of frosting. Chill for 2 hours or overnight.
  19. Add a thin layer of black frosting around the sides of your cake. It doesn’t need to go all the way up the top or bottom, those will be covered. Use a pointed offset spatula to add layers of all the frosting colours, starting with the darkest colours and finishing with the blue and pink frosting. You really won’t need very much frosting at all for this part. It’s all about layering thin bits of frosting over each other.
  20. Sprinkle some white caviar sprinkles over the galaxy to give it a starry night effect.
  21. Add the mint green frosting to a piping bag fitted with a Wilton #8 piping tip. Pipe some jagged edges at the very top and bottom of the cake. Fill the remaining gaps with more frosting. You don’t want to go too down from the top or too up from the bottom because as you use a bench scraper to go around the cake and smoothen out the frosting the frosting will spread over the galaxy and you don’t want to cover up too much of your masterpiece.
  22. Add some frosting up top and use the bench scraper to smoothen it out.
  23. Add the remaining frostings into separate, small piping bags.
  24. Lay out a large piece of plastic wrap on your work bench and pipe lines of each coloured frosting on top, alternating between each one.
  25. Fit the end of a large piping bag with a Wilton 6B piping tip. Frost swirls of frosting on top of your cake and sprinkles with caviar sprinkles.