Vanilla Cardamom Shortbread Snowflake Sandwich Cookies with Espresso Buttercream Filling

INGREDIENTS

2 cups

butter

1 cup

confectioners (powdered) sugar

3 cups

all purpose flour

1/2 cup

arrowroot ( or corn) starch

1/4 tsp

sea salt

1 tsp

ground cardamom

Vanilla bean seeds from 4 vanilla beans ( 1 1/2 tsp vanilla bean seeds)

1 tsp

vanilla extract

1/2 cup

espresso

1/2 cup

sugar

egg whites

1 1/2 cups

butter (3 sticks)

3/4 cup

granulated sugar

1/2 tsp

salt