Preheat oven to 350° F. Line baking sheets with parchments or silpats (see note) and set aside.
In a large bowl, combine dry ingredients (flour, baking powder, baking soda, and salt). Set aside.
In the bowl of a stand mixer, beat butter, sugar, and brown sugar until light and fluffy. Scrape down the sides of the bowl.
Add egg and Irish cream and beat until incorporated. With the mixer running on low, gradually add the dry ingredients. Mix until just incorporated. Fold in chocolate chips (see note).
With a large cookie scoop (see note), scoop dough onto prepared baking sheets at least 2 inches apart. Bake 12 minutes, turning the baking sheet around halfway through. Allow cookies to cool completely on a wire rack.
For Buttercream:
Cream room temperature butter and sifted powdered sugar until well mixed and smooth.
Add Irish cream (see note) and mix to incorporate. If the buttercream is too thin, you can add more powdered sugar to thicken it. If it seems too stiff, more cream can be added until the buttercream is the desired consistency.
For Assembly:
Turn half the cookies over and pipe the buttercream onto each cookie. Top with the remaining cookies to make sandwiches.Enjoy!
Notes
Note on Irish Cream: The store-bought Irish cream that you have on-hand is perfect for this recipe. If you'd like, you can make it homemade! I made homemade Irish cream using the recipe from Smitten Kitchen. The flavor is outstanding! It is a super easy recipe to whip up, and I highly recommend it!Note on cookie scoop: I used a large cookie scoop (about 3 tablespoon volume) to portion out my cookies so they’re all uniform in size (and my hands stay a lot cleaner).