This cake is similar to my Rainbow Layer Cake. Full instructions for making the Rainbow Layer Cake can be found here.
I made this cake for Linda’s birthday. Her husband secretly ordered it from me and I thought that such a romantic gesture wouldn’t be complete without some love hearts!
It really is as simple to make as the photos look – you dye the cake batter, pour into the pans and bake!
Two things make this cake special
1. The Rainbow Inside. A really big surprise if the recipient and/or guests have no idea what is inside.
2. The cake is based on a White Chocolate Mud Cake. Lots of people are scarred to use colours with Chocolate mud cakes if they do not have the special chocolate colours. I did a lot of research before I used my ordinary food colours and the reason they work is because we are not colouring 100% pure chocolate. The other ingredients magically make it alright to use Wilton or AmeriColor (these are the only two makes that I have tried so far).
7″ White Chocolate Mud Cake (Planet Cake recipe)
I used 2 x 7″ pans
180g butter
180g white chocolate
160ml water
195g SR flour
180g plain flour
240g caster sugar
2 eggs, lightly beaten
1 tsp vanilla essence
Ganache
780g white chocolate, finely chopped
270g pure cream
Sugarpaste
730g yellow sugar paste
small amounts of orange, red, purple, blue and green sugar paste
White Chocolate Mud Cake Method
- Preheat the oven to 180C.
- Grease and line bases of both cake pans with baking paper.
- Combine chopped butter and water in a saucepan.
- Stir over low heat until butter is melted. Turn off heat, then add the chocolate and stir until it has melted and is well combined.
- Sift flours into a bowl. Add sugar, a pinch of salt and make a well in the centre.
- Pour chocolate mixture, egg and vanilla into the well then stir with a wooden spoon until well combined.
- Divide the batter equally amongst the 6 bowls. Weigh your mixing bowl before you begin adding ingredients and then subtract the weight of the bowl from the final measurement after the batter is completed. Divide that number by six and add that weight of batter to each bowl, and then whisk a fair amount of the appropriate food colour into each bowl. Keep in mind that the color of the unbaked batter will be the color of the baked batter.
- I poured 5/6th of the red batter into the pan that would be the top tier. I spread it out a little to touch the sides of the pan and be a little thinner in the middle.
- I then poured 4/6th of the orange batter in the middle of the pan on top of the red. I moved it about a little to make a good circle.
- I then poured 3/6th (i.e. 1/2) of the yellow batter on top followed by the green, blue then purple.
- In the second pan that would be the bottom tier, I first of all poured 5/6th of the purple batter followed by the blue, green, yellow, orange and finally red.
- Bake for 30 -35 minutes or until a skewer comes out clean when poked into the middle of the cakes.
- Leave in tins to cool completely on a wire rack.
- When cool, cut the domes off both cake and sandwich together with white ganache making sure that the bottom tier is placed upside down to create the design in my picture at the top of this post.
White Ganache
1. Place chocolate pieces in a large bowl.
2. Put the cream in a saucepan and bring to boiling point. Pour the cream over the chopped chocolate and mix with a hand whisk until the ganache is smooth.
3. Allow to cool completely and then leave to set overnight, if possible.
cakes 
Beautiful!
Thank you.
This is great! I’ve never cooked a cake like this before and will be trying for my boys 1st on the 30th of this month. Out of curiosity (and as Ive never used rolled fondant – sugar paste) is there anything else that you could cover the cake with? 🙂
You could use a firm buttercream to replace the sugar-paste. In fact you could replace both the ganache and the sugar-paste with buttercream.
Cheers
Bernice
what a beautiful cake, and really quite simple to make, thank you for posting
What kind of white chocolate do you use for the ganache? Eating, cooking or melts? Thanks
Nestles Melts
Thank you for you reply. Just a quick question have you made and used marshmellow fondant to cover cakes with and if so did you find it easy to use and does it look nice?
Not tried it but have made Italian and French meringue buttercreams and they are magic.
Sorry I have made ganache a few times but hasn’t worked out. After you have refrigerated overnight if I wanted to cover a cake with it then cover with fondant do you just bring back to room temp then use or do you heat up or whip? Can you whip it for piping as well? Also how long does it last on a cake under fondant? Thanks
After the ganache comes out the fridge you need to bring it back to a workable consistency. You can either microwave it carefully or leave it to get back to room temperature naturally. Stir ganache to return to smoothness but do not whip as whipping introduces air and bacteria to the ganache. Only ever whip ganache if it is to be eaten the same day and is kept at food safe temperatures.
Non whipped ganache will last a week or more under fondant.
Cheers Bernice