Sugar Cookie Bars with Chocolate Buttercream

INGREDIENTS

For the cookie bars:

2 cups

(10 ounces*) all-purpose flour

1/2 tsp

baking powder

1/4 tsp

salt

1 cup

unsalted butter, at room temperature

1 cup

sugar

1 tbsp

brown sugar

egg, at room temperature

1 1/2 tsp

pure vanilla extract

For the chocolate buttercream:

1/2 cup

unsalted butter, at room temperature

3 cups

powdered sugar

3 tbsp

milk, at room temperature

1 tsp

pure vanilla extract

1/8 tsp

salt

4 oz

unsweetened chocolate, chopped, melted, and cooled to room temperature