-7 layer sponge:
7 egg whites (medium)
2 cups sugar
1 cup unsalted butter, melted
2 teaspoons vanilla extract
1 cup milk, room temperature
1/2 cup sour cream
3 cups plain flour
3 teas baking powder
1/4 teaspoon salt
Food colours: Yellow, Red, Blue
3 cups milk
1 cup sugar
5 tbs flour
2 tbs corn flour (starch)
mint oil, or other flavouring
1 teas vanilla
500 gr butter, room temperature
Prepare as many 22 cm tins, as you have (I had two); line with baking paper, and make some extra baking liners ready (I had 4). Preheat oven to 160*C (fan forced).
Beat egg whites with a high speed, until you get a stiff foam. Add sugar, spoon by spoon, mix well. Pour butter, milk, sour cream and vanilla. Mix until all incorporated. Switch mixer off, and sift flour, baking powder and salt on top of meringue. Fold in with spatula. Divide mixture into 7 little bowls, and let the fun begin: in each bowl add food colouring until you're satisfied with shade. Be careful - use pipette or similar. Bake each colour sponge separately, 10-12 min. Repeat if you don't have 7tins. Let it cool.
Mix flours with a little milk until smooth and silky.
Put the rest of the milk and sugar into a saucepan, bring to boil. Pour flour/milk mixture into boiling milk, and cook on slow heat, until thick. Let it cool completely (not in refrigerator).
Beat butter well, add 'custard' and beat together until you get smooth creamy texture. Top each sponge/layer with this icing, take care to put layers in order, and then spread icing on top and around the cake.
Hide colours well; it makes a nice surprise for a cutting/celebrating person when they realise all the colours inside
Pairs Well With
I avoid using artificial colours or additives in my food, but once a year it is OK, especially if it's someones wish to have it for their Birthday.
One other reason is the 'wow' factor that you get when cutting this cake.