Salted Egg Yolk Cupcakes with Salted Egg Yolk Butter Cream

The Cupcakes
4 eggs
1 1/4 cup cake flour
1 1/4 cup all purpose flour
1/2 cup Knorr salted egg yolk powder
1 cup buttermilk
1 1/2 cups granulated sugar
2 teaspoons baking powder
225g unsalted butter, softened, cut into small cubes

Method
1. Preheat the oven to 160ºC.
2. Mix the flours, knorr salted egg yolk powder, sugar and baking powder in a mixing bowl and combine well.
3. Add the butter and mix on low speed. 
4. Add the eggs, one by one and scrape the bottom of the bowl to make sure all the ingredients are well-combined.
5. Add 1/2 of buttermilk into the mixture and beat for 1-2 minutes. scrape the bottom and sides of the bowl. Add the rest of the buttermilk and beat for another 1-2 minutes (do not over mix).
7. Scoop the batter into the cupcake liners till 2/3 full and bake for 20-30 minutes.
8. Cool completely on wire rack before frosting.

The Buttercream
3 egg whites
1/2 cup Knorr salted egg yolk powder
1 cup granulated sugar
225g unsalted butter, softened but cool

Method
1. Place the egg whites and sugar in a mixing bowl. Set it over a pot of simmering water (the water should not touch the base of the bowl) and whisk continuously, until the sugar is completely dissolved and remove.
2. Whip the mixture on high speed till stiff peaks form.
3. Add the Knorr salted egg yolk powder and mix till just combined. 
3. Beat 225g butter into the beaten egg whites in 3 batches. The mixture will look watery, just continue beating until the mixture become creamy.
4. Lastly, add in 1/2 cup of Knorr salted egg powder and continue beating till the buttercream is smooth.