Fluffy Vanilla Birthday Cake with Sprinkles

Vanilla Cake

cake flour (sifted (345 g))

granulated sugar (400 g)

baking powder (17 g)

salt (2.5 g)

large egg whites (at room temperature (150 g))

whole egg (at room temperature)

whole milk or full fat buttermilk at room temperature (237 ml)

pure vanilla extract (12 ml)

unsalted butter (cold and cut into 24 even pieces (170 g))

Vanilla Buttercream Frosting

unsalted butter, softened to room temperature

sifted confectioners' sugar

pure vanilla extract

Seeds scraped from one vanilla bean (or add 1 more teaspoon of pure vanilla extract)

heavy cream

salt

Decorations

Sprinkles (I used about 1 cup of rainbow jimmies)