12 Tbsp butter, softened
2 cups powdered sugar
½ cup granulated sugar
7/8 cup egg whites (from 6-7 eggs)
2 Tbsp vanilla extract
1 1/2 cups gluten free all purpose flour
1/2 cup heavy cream
8 oz semisweet chocolate, chopped
Preheat oven to 350 F and line four or more baking sheets with silicone mats or parchment paper (use as many baking sheets as will fit in your oven).
In a large bowl or bowl of a stand mixer, cream the butter. Add sugar and mix until combined.
Add egg whites gradually, then mix in the vanilla. Add flour and mix until just combined.
Using a piping bag fitted with a 1/4 plain tip (#12), pipe 2-inch sections of batter onto the baking sheets about 2 inches apart. Bake in oven for 10 minutes or until edges are a light golden brown. Remove from oven and let cool completely on baking sheet.
To make the filling: In a small saucepan, scald the heavy cream (bring it to about 180 degrees F). Pour scalded cream over chopped chocolate in a large bowl and whisk to melt.
Spoon a thin layer of filling on the flat side of half the cookies. Press the flat side of another cookie down lightly on top of the filling. Repeat with remaining cookies. Place cookies in refrigerator for 10 minutes to set filling.