• Pre-heat oven to 350°F and line two cookie sheets with parchment paper. Set aside.
• In a medium bowl, whisk together the flour, cocoa powder, espresso powder, baking soda, and salt. Set aside.
• Melt the dark chocolate in a double boiler. For a double boiler, place some water in a large saucepan and bring to a light simmer. Place a heat-safe bowl on top of the pan and stir chocolate chips until melted. Let cool.
• Place the softened butter and sugars in a stand mixer fitted with the paddle attachment. Mix on high speed until fluffy and lighter in color. About 2-3 minutes. Mix in the melted chocolate.
• After scraping down the sides, add the egg and the vanilla extract. Mix until combined. 
• After turning the mixer to low speed, add the flour-cocoa mixture. Mix on low speed until just combined. Do not over mix!
• Turn off the mixer. Gently fold in the chocolate chips with a wooden spoon or spatula until combined. 
• Using a 2″ cookie scoop, drop scoops about 2 inches apart. Bake for 11 minutes. Cool on the tray for about 7 minutes before transferring them to a cooling rack. Completely cool before assembling the sandwich cookies. 

Marshmallow Cream Cheese Filling

Add all the softened filling ingredients to a large mixing bowl, and beat until smooth and fluffy. About 2-3 minutes.