Cake:
1. Preheat the oven to 180°C. Grease and line 2 x 20cm round cake tins with baking paper.
2. Using an electric mixer or stand, cream together the butter and sugar for 3-5 minutes until light and fluffy.
3. Add the eggs, one at a time, mixing well after each addition and scraping down the bowl occasionally.
4. In a separate bowl, combine the Lancewood Double Cream Vanilla yoghurt with the milk and mix until smooth.
5. In another bowl, mix the flour and baking powder.
6. Add a third at a time of the flour and yoghurt mixture to the creamed mixture, alternating each time and mixing gently after each addition. Do not overmix the batter as the batter will be mixed again when the colours are added.
7. Divide the batter equally between 4 bowls. Add about 10 drops of each food colouring to each of the bowls. Mix as gently as possible until the batter is evenly coloured, adding more colour if desired.
8. Pour two of the coloured batters into prepared tins and bake for 30 - 35 minutes or until a skewer inserted into the center of the cake comes out clean.
9. Cool for 5 minutes in the tin, then remove and place on a cooling rack to cool completely. Clean the tins then grease and line them again. Repeat the baking process with the remaining 2 coloured batters.
Icing:
1 Beat the butter until light and creamy, then gradually add the icing sugar, beating well after each addition.
2. Add the vanilla essence and milk or cream and beat well until light and fluffy.
To assemble:
1. Once all the cakes have cooled completely, trim the tops of the cakes.
2. Place the blue cake onto a cake stand or cake turntable if you have one. Spread a fairly thick layer of icing over the cake, then place the green cake on top and repeat. Place the yellow cake on top and repeat, then finally top with the red cake.
3. Using a palette knife, coat the top and sides of the cake in a thin coat of icing. Refrigerate for at least 1 hour until the icing is set hard. This is called a crumb coat and seals in all the loose crumbs so that the final cake is nice and neat.
4. Spread a thick layer of icing over the whole cake, and smooth as neatly as possible with a palette knife. Chill for about 30 minutes.
To decorate:
1. Make a semi-circle with red Smarties starting close to the edge of the cake. Repeat with a semi-circle of orange Smarties, directly under the red. Continue to make a rainbow using the yellow, green blue and purple Smarties.
2. At the base of each end of the rainbow, use the white mini marshmallows to create a cloud shape.
3. Slice and enjoy!
