In a small saucepan over medium-low heat, melt the chocolate chips and butter. Once melted, remove from heat, stir in vanilla extract and set aside to cool.
Add in the flour mixture and fold until combined. Chill cookie dough in fridge for at least 10 minutes so batter can thicken and look more like cookie dough.
While the cookies bake, combine the powdered sugar with the melted butter, cocoa, espresso and salt. Stir until combined. Add a splash more coffee or water to get desired consistency.