Rainbow sprinkles/100s & 1000stwo-three packets should be enough!
Preheat the oven to 180°C then grease and line three deep 6” round tins.
In a mixer, beat together the butter and sugar until light and fluffy.
Add the vanilla and then gradually incorporate the eggs, mixing the batter between each addition to ensure the mixture doesn’t split. Don’t worry if it does, just add a tablespoon of your flour and this will help pull it back.
Once the eggs have been fully incorporated, add the flour and baking powder; fold in the dry ingredients gently.
Add the sprinkles at the very last moment; quickly fold them in and then split the mixture between the three tins.
To ensure your cakes come out flat, make a well (about 2cm deep) in the middle of the batter. That way, when the centre rises, it will rise to the level of the rest of the cake!
Bake for approximately 30 minutes or until golden brown. A skewer pierced into the centre of the cake should come out clean.
Once baked, turn the cakes out onto a wire cooling rack and leave overnight if possible. I find sponge cakes are much easier to cut and decorate if they’re a day old.
Smooth and steady
Make your buttercream, using your favourite recipe. If you don’t have a favourite, feel free to use mine which can be found here.
You need to make about 1.5kg of buttercream to fill and crumb-coat the cake (yes, I know, but it’s a large cake and it will serve a lot of people! You can also freeze any leftover buttercream for later use.)
I usually start by spooning a small amount of buttercream on my cake board, which I spread slightly before placing the first layer onto the board. This ensures the cake is stuck to the board and doesn’t move around when you start to ice it!
Spread a sufficient amount of buttercream to coat each layer thinly (about a 2mm thickness) before stacking them. I tend not to overfill the layers as this can lead to instability and can also cause the filling to ooze out when you’re trying to smooth the sides later.
Once stacked and filled, place the cake into the fridge for about 30 minutes to an hour to firm up before crumb-coating the whole cake (top and sides.) When you crumb-coat, you’re not looking to create a super smooth finish; you simply want to spread a thin layer of buttercream onto any exposed cake to catch any crumbs which would otherwise end up in the final finish.
Place the cake bake into the fridge, preferably overnight, until the buttercream has dried down and ‘crusted’.
The next day, it’s time to ice your cake with it’s final layer.
Let’s get colourful…
I use a Wilton #789 tip to apply a layer of buttercream over the entire cake before using my icing smoother to create a smooth finish.
Holding the icing smoother at 90° to the turntable, at a 45° to the cake. In one smooth rotation, turn the cake so that the smoother removes a layer of icing
Repeat, cleaning any icing from the smoother between each rotation, until the icing on the sides is smooth.
Smooth the top in a similar way before patting sprinkles around the base of the cake.
Return the cake to the fridge to let the buttercream form a crust.
Once dry to the touch, the cake is ready to glaze with royal icing. If you don’t have a preferred recipe for royal icing, I would suggest using my recipe here.
Split the icing into five bowls, and colour each with one of the following colours: red, orange/yellow, green, blue, purple.
Pour the icing onto the top of the cake in sections, helping it to drip down the sides.
Once there is sufficient drippage, use a cocktail skewer to swirl a marble pattern into the top.
Place the cake back in the fridge to set before serving.