INGREDIENTS
1
and 3/4 cups (200g) cake flour1
3/4 tsp
baking powder
1/4 tsp
baking soda
1/4 tsp
salt
1/2 cup
unsalted butter, softened to room temperature
1 cup
granulated sugar
3
large egg whites, at room temperature
2
teaspoons pure vanilla extract2
1/2 tsp
butter extract3
seeds scraped from 1/2 of a vanilla bean2
1/2 cup
full-fat sour cream at room temperature4
1/2 cup
(120ml) whole milk at room temperature4
1/2 cup
rainbow sprinkles5