Preheat oven to 375 degrees. Line your baking sheets with parchment paper.
Whisk together the dry ingredients and set aside.
With your mixer, cream the butter and both sugars; add the egg.
Add the flour mixture alternately with the Bailey’s Irish Cream –beginning and ending with the flour mixture. Add the vanilla.
Drop by tablespoonfuls on your baking sheet 2 inches apart.
Bake 10-12 minutes and cool on pan another 5 minutes.
Remove cookies to wire rack to cool completely.
Make the filling: Combine butter and sugar and beat at medium speed until light and fluffy, about 3-5 minutes.
Add Baileys next and beat until combined.
Place filling in a piping bag fitted with a large star tip.
Pipe the filling onto 1/2 of the cookies and top with the remaining ones.