Portion: Makes 2 to 3 dozens
1.5 cup unsalted butter, room temperature
2 cup icing sugar
3/4 cup cocoa powder
2 tsp vanilla extract
2 egg yolk
2 tbsp milk
3 cups all purpose flour
1/2 tsp salt
1/2 tsp baking powder
2 egg white
1/3 tsp peppermint extract
4 cups icing sugar
Beat butter until smooth and fluffy.
Sift together icing sugar and cocoa powder over butter and beat in. Stir in vanilla, egg yolk and milk. Add flour, salt and baking powder and blend until incorporated. Shape dough into a disc, wrap with plastic warp and chill for 20 minutes.
Preheat oven to 350F.
On a surface slightly dusted with icing sugar, roll out dough to 1/8 inch thick. Cut into desired shapes and transfer carefully to a parchment-lined baking sheet. Bake for 12-15 minutes, until cookies can be lifted easily away from the parchment. Allow to cool completely on baking sheet.
Put egg white in mixing bowl. Add peppermint extract and mix well. Beat in icing sugar, a few tablespoonfuls at a time, until a soft dough forms. You may not need to use all icing sugar.
To fill cookies, roll a teaspoon of dough into a ball and flatten with the palm of your hand. Sandwich between 2 cookies and press together carefully.
Always sift cocoa powder as it always has lumps!