Rainbow Cake

Rainbow Cake
Rainbow Cake

This cake is similar to my Rainbow Layer Cake. Full instructions for making the Rainbow Layer Cake can be found here.

A slice of Rainbow Cake
A slice of Rainbow Layer Cake

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!

It is based on a white mud cake, filled with white chocolate ganache and covered in sugar paste
This cake was so much fun to make and eat!  I love the surprised look on peoples faces when you pull out the first slice ~ Rainbow cake is something that makes everyone smile 🙂
If you need more information on how to make ganache and cover your cake with it just click here.

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

    1. Preheat the oven to 180C.
    2. Grease and line bases of both cake pans with baking paper.
    3. Combine chopped butter and water in a saucepan.
    4. 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.
    5. Sift flours into a bowl. Add sugar, a pinch of salt and make a well in the centre.
    6. Pour chocolate mixture, egg and vanilla into the well then stir with a wooden spoon until well combined.
    7. 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.
    8. 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.
    9. 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.
    10. I then poured 3/6th (i.e. 1/2) of the yellow batter on top followed by the green, blue then purple.
    11. 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.
    12. Bake for 30 -35 minutes or until a skewer comes out clean when poked into the middle of the cakes.
    13. Leave in tins to cool completely on a wire rack.
    14. 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.

Colours of the rainbow
Colours of the rainbow
Coloured cake batter
Coloured cake batter
Ready for the oven
Ready for the oven
Cooling on a wire rack
Cooling on a wire rack
Rainbow Cake
Rainbow Cake
Rainbow Cake
Rainbow Cake
Rainbow Cake
Rainbow Cake
Rainbow Cake
Rainbow Cake
Rainbow Cake
Rainbow Cake
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How to make a Rainbow Layer Cake using white chocolate mud recipe

Rainbow Cake
Rainbow Layer Cake

This cake is similar to my Rainbow Cake below and you can find full instructions for it here.

Rainbow Cake
Rainbow Cake

Three things make this cake special

1. The Rainbow Layers. They can be a 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).

3. You can make this cake even if you do not have 6 x 10″ round cake pans. I have 2 x 10 inch pans and I bake the layers in 3 batches. You could make do with just one pan, it will just take a little longer.

Colours of the rainbow
Colours of the rainbow Red, Orange, yellow, green, blue and purple.
Coloured cake batter
Coloured cake batter
Use 2 x 10 inch pans
Use 2 x 10 inch pans

White Chocolate Mud Cake 

(Planet Cake recipe)

Need a minimum of one 10″ pan ( 6 x 10″ pans would make the job really easy though!)

I used 2 x 10″ pans as that is all I have.

390g butter
390g white chocolate
350ml water
195g SR flour
390g plain flour
520g caster sugar
4 eggs, lightly beaten
2 tsp vanilla essence

White Chocolate Mud Cake Method

  1. Preheat the oven to 150C.
  2. Grease and line bases of both cake pans with one thickness of baking paper.
  3. Combine chopped butter and water in a saucepan.
  4. 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.
  5. Sift flours into a bowl. Add sugar, a pinch of salt and make a well in the centre.
  6. Pour chocolate mixture, egg and vanilla into the well then stir with a wooden spoon until well combined.
  7. 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 color into each bowl. Keep in mind that the color of the unbaked batter will be the color of the baked batter. Pour into the pans and bake for 15 minutes each or until a skewer comes out clean when poked into the middle of the cake.
  8. Once cake pans have been washed, repeat the process twice more till all 6 layers have been baked.

 

Rainbow layers ready for buttercream
Rainbow layers ready for buttercream

Lemony Swiss Meringue Buttercream

As you can see from the recipe, this cake requires a huge amount of buttercream to fill the layers and cover the outside. I would recommend that you make the buttercream in two separate batches ( 1. To fill and crumb coat. 2. To frost) because you would need a HUGE bowl to make this much buttercream at one time!

Please click here for a step-by-step guide to making Swiss Meringue Buttercream and troubleshooting tips!

To fill and crumb coat:

9 egg whites
1 ¾ cup (350 g) sugar
4 sticks (452 g) butter, room temp
2 tsp lemon extract

To frost:

5 egg whites
1 cup (200 g) sugar
2 sticks (226 g) butter, room temp
1 tsp lemon extract

Cook the egg whites and sugar in a small saucepan over medium heat, whisking constantly, until the sugar is completely dissolved (test by rubbing some between your fingers. If it’s completely smooth, it’s done). Pour into another bowl (a stand mixer is preferable) and whip on high speed until room temp. Then, on a medium-slow speed, add the butter, waiting until each piece is completely incorporated before adding the next. After all the butter has been added, turn the mixer back to high speed and whip until it has come together, about five minutes. Add the extract, beat briefly and then use.

If the buttercream seems soupy after all of the butter is added and does not come together after whipping, refrigerate for 5 to 7 minutes and continue whipping until it becomes fluffy and workable.

Filled with buttercrem
Filled with buttercrem

Assembly

Stack the layers in your preferred order and fill and frost as you would any other cake.

Once frosted, the cake can be left on the counter without any problems, but feel free to refrigerate it. Just be sure that the cake is at room temperature when serving or the frosting will be hard.

A slice of Rainbow Cake
A slice of Rainbow Cake