Please note: To make the 6 layered cake you see pictured; you’ll need to double the cake recipe only. All other measurements are enough to fill, crumb coat and finish decorating the cake.Preheat a fan-forced oven to 140°C (275°F) or a conventional oven to160°C (320°F). Spray three 20 cm (8 in) cake tins with oil spray and line the bottoms with baking paper. Set aside. Add the flour, sugar, baking powder and salt to a large mixing bowl and mix with a hand mixer until well combined.
Next, add the softened butter and mix on low speed until the mixture reaches a crumbly, sand-like texture.
Add the eggs, milk, oil, Greek yoghurt, boysenberry flavouring and vanilla, and mix on low speed until all the dry ingredients are incorporated. Scrape down the side of the bowl and mix for another 20 seconds.
Split the batter into four separate bowls. Colour each one in the three different colours using the colour combinations listed in the ingredients list.
Add each coloured batter into a separate piping bag and pipe little squiggles of the batter in each cake tin alternating between each one.
Bake for 50–60 minutes, or until a toothpick inserted in the middle a cake comes out clean. If the toothpick is coated with wet batter, continue baking, for 10 minutes at a time, until fully baked.
Allow the cakes to cool to room temperature in the tins, then chill them in the fridge overnight. Chilling your cakes overnight makes them easier to trim and decorate, so I always bake my cakes the day before I decorate them.
To trim your chilled cakes, use a cake leveller or large serrated knife to carefully trim the crust off the top of each cake before you trim each cake in half. You’ll end up with 6 layers of cake.
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.
Add the purple 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.
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.
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.
Add the black and green frosting into two separate piping bags and frost the cake with black frosting to begin with. Use a cake scraper to spread the frosting around the top and sides of the cake. It doesn’t have to be 100% perfect but just make sure it’s fairly even. Then frost some of the green frosting on the top and sides of the cake and repeat. Pop it back in the fridge for 3 hours to chill completely.
Now the fun part! Making the galaxy! This part is all about layering.Layers upon layers upon layers! So just have fun with it. I used some sponge brushes. I bought them from my local craft supply store. Just give them a wash before you use them. Go around the cake layering each colour on top of one another until you’re happy with the galaxy effect.
To finish the cake, add the sugar crystal rock sprinkles at the darkest spots of the cake to make them look like space rocks floating around your cake!