A Homemade Kitchen: Oreo Cookies

INGREDIENTS

For the cookies::

1 1/4 cups

all-purpose flour

1/2 cup

unsweetened Dutch-process cocoa powder

1 tsp

baking soda

1/4 tsp

baking powder

1/4 tsp

salt

1 cup

granulated sugar

1/2 cup

plus 2 tablespoons (1 1/4 sticks) unsalted butter, at room temperature

large egg

For the filling::

1/2 cup

unsalted butter, at room temperature

2 cups

sifted confectioners' sugar

2 tsp

pure vanilla extract