Preheat oven to 350 degrees Fahrenheit
In a stand mixer, beat melted butter, room temperature butter, and both sugar until completely creamed together ~ 3 minutes.
Add in egg and vanilla extract, beat until combined together.
Add in kosher salt, baking soda, cocoa powder, and all purpose flour. Beat until just combined. Use a silicone spatula to make the dough is fully combined.
Scoop cookie dough using a 1.5 tablespoon scoop onto a silicone mat lined on a baking sheet. Leave about an 1-2 inches between each cookie. Bake for 8 - 10 minutes in a pre-heated oven.
After removing from the oven take a bottle of vanilla extract, turn upside down and gently push the cap into the center of the cookie for a few seconds making sure not to push all the way down but enough to create a small well. Cool cookies to room temperature.
Fill a small sauce pot with an inch or 2 inches of water. Heat on the stove until simmering. Place a small metal bowl on top of the pot and fill with heavy cream, Bailey's Irish Cream, butter and chocolate chips. Melt and whisk together until completely combined.
Let the ganache cool slightly and fill a piping bag. Snip off the end and fill each cookie to the top. Let the ganache set and cool.
Melt chocolate wafers according to package directions.
Drizzle chocolate over the cookies using a snipped piping bag/sandwich bag or spoon. Finally, sprinkle each cookie with a pinch of flaky sea salt. Let the chocolate set and enjoy!