Preheat oven @180C for 15 minutes.
Grease 3 round 6 inch cake tins.
Keep all ingredients ready at room temperature.
Sift together flour, baking powder and soda
In a mixing bowl beat together milk, curd, butter sugar and vinegar. Mix dry and wet mixture.
Divide batter in three equal parts. Mix 1/2 tsp green food colour and 1/2 tsp mint essence in one part. Pour in one cake pan.
Mix 1/2 tsp vanilla essence in one part. Pour in one cake pan.
In the third part add 1/2 tsp orange food colour and 1/2 tsp orange essence. Pour in one cake pan.
Bake cakes in the oven for 20 minutes.
Check if cakes are cooked by inserting a skewer in the middle. It should come out clean.
Cool the cakes on wire rack for some time. Cling wrap and refridegrate to cool for 1 or 2 hours.
For butter-cream frosting keep butter on kitchen counter for atleast 3 hours to soften naturally. Do not heat or melt the butter.
Sift icing sugar for lumpfree and smooth butter cream.
Take butter in bowl and beat till light and fluffy for atleast 8-10 minutes.
Now add icing sugar spoon by spoon and let it incorporate and keep beating on slow speed. Till you add all the icing sugar.
Divide the butter-cream in three portions. Keeping more for orange colour if you are following my design.
Add 1/2 tsp orange essence and 1/2 tsp Orange food colour to the larger portion and mix
Add 1/2 tsp green food colour and 1/2 mint essence to one bowl and mix.
For white I added some white food colour as the buttercream looks pale in colour. You may avoid using if you want.
Assembling the cake. Slice the uneven top part of cake using a serrated knife or leave it as it is, if you like.
Apply buttercream on cake board so the cake sticks properly and does not slide while decorating.
Place the green mint sponge. Apply mint butter cream and spread evenly making a thin layer of frosting.
Place white vanilla sponge and apply vanilla buttercream and spread.
Over this place orange sponge and spread white buttercream all over cake. To crumb coat the cake with thin later of frosting.
Keep the cake to chill for 10-15 minutes in refridgerator.
Fill the buttercream in different disposable piping bags and keep them ready.
To make rossets like I have done you will need nozzle N2.
Prepare a piping bag with the nozzle fitting. Place green frosting bag first to pipe green rossets. Try one on a plate and then start working on cake.
Go antilock direction with steady hands.
Now take white butter cream and repeat the same design. Try to make rossets in the centre of the earlier 2 green ones, so no gaps can be seen.
Repeat with the orange buttercream and cover the whole cake. Try to do it as even as possible.
Tri Colour Butter Cream cake is ready to serve