1 & 1/2 cups all-purpose flour
1 teaspoon baking powder
1/2 teaspoon baking soda
1/4 teaspoon salt
3/4 cup unsalted butter, softened
1/2 cup packed light brown sugar
2 large eggs
seeds of 1 vanilla bean or 1 tablespoon vanilla bean paste or vanilla extract
1/2 cup sour cream
5 tablespoons unsalted butter
1 cup confectioners' sugar
2 to 4 tablespoons milk
1/3 to 1/2 of the seeds of 1 vanilla bean or 1 teaspoon vanilla bean paste or vanilla extract