Line two baking sheets with parchment paper.
In a bowl, whisk together cocoa powder, salt, and powdered sugar. Pour in a little powdered sugar at a time to easily incorporate the ingredients. Add in egg whites and vanilla extract until all the batter is moist.
The batter will resemble brownie batter and be thick. Next stir in the semi-sweet chocolate chips and use your arm muscles to fully mix.
Use a cookie scoop to spoon the batter onto the parchment lined baking sheets. If you do not have a cookie scoop use a spoon to place about one tablespoon of batter per cookie on the baking sheet.
You should have about twelve cookies per baking sheet.
Let the cookie batter rest on the baking sheets at room temperature for thirty minutes. This is a super important step. It helps the cookies form into the correct shape when they bake.
While your cookie batter is resting begin making your Baileys salted caramel buttercream.
Put the room temperature unsalted butter, caramel sauce, Baileys, and salt in a mixing bowl. If you'd like a non-alcoholic dessert simply leave out the Baileys. Use an electric mixer or hand-held mixer to beat the butter and caramel sauce for about one minute. The texture of it should be light and whipped.
Slowly fold in the powdered sugar to the mixture. Once it is folded in, use your mixer to fully incorporate.
If the buttercream becomes too thick add a dash of milk or cream and mix until it is smooth.
Set buttercream aside and cover with plastic wrap.
Preheat oven to 350 degrees. Once your cookie batter has rested for thirty minutes, they are ready to bake.
Bake cookies for ten-twelve minutes. The top of the cookies should be glossy and cracked. The edges will be set and the middle slightly undercooked.
Have the cookies cool on the baking sheet for about twelve minutes before transferring them to a cooling rack to finish cooling.
As the cookies cool, scoop your buttercream into a piping bag. I used an open star piping tip to pipe the buttercream for the filling. You are welcome to use any piping tip you'd like. Be creative!
Pipe the buttercream on the bottom side of one cookie. Lightly place another cookie on top to sandwich the filling. Take your course salt and sprinkle it around the outside of the cookie onto the buttercream.
Enjoy and eat responsibly!