Preheat the oven to 350°F. Line a baking sheet with a silicone baking mat or parchment paper and set it aside. Get a bowl and put the ¼ cup of granulated sugar for rolling the cookie dough in and set aside.
Cream together the butter, brown sugar, and granulated sugar until light and fluffy; about 1-2 minutes. Beat together for about a minute until light and fluffy. Add the egg and vanilla extract, and mix until combined.
Add in the flour, cocoa powder, baking soda, salt, and espresso powder. Mix one more time until the dough forms.
Using a small cookie scoop, scoop dough and roll into balls. Once rolled into balls, roll into the granulated sugar, and place on the prepared baking sheet, about an inch and a half apart.
Bake the cookies for 8-9 minutes. The indents will have puffed up a bit, so you will have to slightly press them down again with the ¼ teaspoon. Allow them to rest about 5 minutes, then transfer cookies to a cooling rack to finish cooling completely. Repeat until all of the cookies are baked.
Add the heavy cream and Irish cream to a microwave safe cup/bowl, microwave for 30 seconds. Give it a quick stir, and microwave for another 30 seconds. Add the chopped milk chocolate to the heavy cream, and let it sit for 5 minutes, giving time for the chocolate to melt. After 5 minutes, add the espresso powder and pinch of salt and mix everything together with a fork or a small whisk. Allow the ganache to cool for about 15-20 minutes. It will thicken as it cools.
Pour the ganache into the indents of the cooled cookies. Allow the ganache to set. You can speed up the process by placing the cookies into the fridge for about 30 minutes to allow the ganache to set. Once set, enjoy!