INGREDIENTS
1 1/2 cups
+ 2 tablespoons all-purpose flour
1/4 tsp
kosher salt
1 1/4 tsp
baking powder
1/2 cup
unsalted butter, room temperature
1 cup
sugar
1
egg plus 2 egg whites
1/2 cup
whole milk
1/4 cup
sour cream
1 1/2 tsp
vanilla extract
1/2
vanilla bean (or one whole bean if you can spare it)
1/2 cup
unsalted butter, room temperature
1 1/4 cups
powdered sugar
1/2
vanilla bean (or 1 teaspoon of vanilla extract)