Best Birthday Cake

INGREDIENTS

For the yellow cake::

2 1/3 cups

all-purpose flour

2 1/2 tsp

baking powder

1/2 tsp

salt

12 tbsp

unsalted butter, at cool room temperature

1 3/4 cups

granulated sugar

large eggs, at room temperature and separated

2 tsp

vanilla extract

1 cup

whole milk

For the milk chocolate buttercream::

6 oz

milk chocolate, melted and cooled

2 sticks

unsalted butter, at room temperature

large egg yolk, at room temperature

1 tsp

pure vanilla extract

1 1/4 cups

confectioners' sugar, sifted

1/4 tsp

fine salt