Red Velvet Cake with Creamy Vanilla Icing

The recipe is from Magnolia cookbook (Magnolia is a famous bakery in NY). I have improvised and put this improvisions in ()

Cake:
3.5 cups of cake flour (I used normal flour but sifted it twice)
0.75 cup of butter
2.25 cups of sugar (I used 2 only and I used pure cane sugar which is not too expensive in Geneva... but in Singapore cannot get also)
3 large eggs at room temperature(I used 4 eggs weighing 53g each)
6 tablespoons of red colouring (the normal red colouring, when you use 6 tablespoons, will give a bitter after taste, what 1 do is use 2 tablespoons of red colouring and add 4 tablespoons of water)
3 tablespoons of cocoa
1.5 teaspoon of vanilla extract
1.5 teaspoon of salt
1.5 cups of buttermilk (I cannot get buttermilk here and was too lazy to make it,so I used a combination of yoghurt and milk... and I think I added in between 0.25 to 0.5 of additional milk)
1.5 teaspoon of baking soda
1.5 teaspoon of cider vinegar

Method

Preheat oven to 350 degrees
Cream butter and sugar until very light and fluffy with electric mixer (about 5 mins). Add eggs one at a time and add beat well after each addition.
Whisk red colouring, cocoa and vanilla and add the mixture to the butter mixture.
Add salt to the buttermilk.
Add the flour in 3 parts alternating with the buttermilk each time. Beat well each time.
Mix the baking soda and vinegar and add to the cake mixture. Mix all very well, scrape the bottom of the bowl to ensure everything is smooth.
Pour mixture into cupcake pan, which is already lined with cases, 0.75 full. I got 24cupcakes with this recipe.

Creamy Vanilla Icing
3 tablespoon of flour
1 cup of milk
1 cup of butter
1 cup of sugar
1 teaspoon of vanilla extract

Method
Whisk flour into the milk in a saucepan. Place mixture on medium heat and stir constantly until it becomes real thick and begins to bubble. Cool it

After it is cool, beat butter until fluffy, then add sugar gradually. Add vanilla. Add cooled milk mixture. Beat well.

Refrigerate for exactly 15 minutes.

Ice/Frost on cooled cakes (only make the icing/frosting after the cake has cooled down).