Preheat oven to 375 degrees F.
In a large bowl sift together the flour, salt, baking soda and espresso powder. Set aside.
In the bowl of a large stand mixer fitted with a paddle attachment, cream together the butter and both sugars for about 3 minutes, scraping down the sides of the bowl as needed to incorporate all the sugary buttery goodness. Next, add the vanilla and Irish cream and beat until combined, about 30 seconds more.
Add the room temperature eggs into the butter mixture one at a time until fully incorporated. Slowly add the dry ingredients into the wet ingredients, and beat just until everything comes together, scraping down the sides of the bowl again if needed. Gently fold in the chocolate chips.
For this recipe I used two 8 inch skillets to make two medium sized cookies. You may also use one large 12 inch skillet if you prefer a larger cookie, but may need to adjust the bake time. Cast iron is recommended, but if you don't have access to cast iron any oven safe skillet will also work well. Using 1 tablespoon of butter per skillet, butter the skillet(s). Divide the dough in half between the two skillets, spreading the dough out evenly with a rubber spatula.
Place the skillets in the oven and bake for 17-20 minutes, until the edges begin to turn golden brown. The key here is to not over bake the cookies! They will seem undercooked, but we want that ooey-gooey chocolate center. As the cookies cool, the middles will become more firm, but will still have a soft, gooey center. While the cookies are baking, make the salted caramel whiskey sauce.