In a medium bowl, whisk the flour, cocoa powder, baking soda, and salt together until combined; set aside.
In a small bowl, combine the instant espresso powder and hot water until completely dissolved; set aside.
In the bowl of an electric stand mixer fitted with a paddle attachment, cream the butter until smooth. Add in both sugars and mix on high for 3 minutes until light and fluffy. Add the eggs one at a time, mixing after each addition until combined. Add in the vanilla and espresso mixture. Then stir in the pudding mix.
With mixer set on low speed, slowly add the flour mixture into the wet mixture until everything has been incorporated.
Preheat the oven to 350ºF and line a baking sheet with parchment paper. Shape dough into balls, and place them onto the prepared baking sheet. Gently flatten each ball to about 3/4 inch in thickness (see photo above). Bake in the preheated oven for 8-10 minutes.
Allow the cookies to cool on the baking sheet for 2 minutes (no longer than 5 minutes) before pressing the bottom of a glass or measuring cup into the center of each cookie, creating an indentation for the filling. Transfer cookies to a cooling rack and cool completely.
Make the Mousse:
In the chilled bowl of a stand mixer fitted with the whisk attachment, beat the 1 cup of heavy cream until soft peaks form. Add the powdered sugar and continue beating until stiff peaks form. Transfer whipped cream to a separate bowl and return bowl to mixer.
Switch the whisk attachment out for the paddle attachment and beat the cream cheese on high until smooth and creamy.
In a separate bowl, combine the chocolate chips and 2 Tablespoons of heavy cream. Heat in the microwave, stopping and stirring every 15 seconds, until mixture is smooth. Pour melted chocolate mixture into cream cheese and beat until combined. Add a third of the whipped cream to the bowl, beating until smooth. Remove bowl from mixer and fold in the remaining whipped cream by hand with a spatula.
Make the Ganache:
Place the chocolate into a medium bowl. Pour the heavy cream into a glass measuring cup, and heat in the microwave until it just begins to simmer. Pour hot cream over the chocolate, cover with plastic wrap, and allow it to sit for a few minutes. Remove the plastic wrap and stir until smooth. Allow to cool to room temperature.
To Assemble:
Divide mousse evenly among each cookie, then use a butterknife or offset spatula to spread evenly. Drizzle each cookie with chocolate ganache. Serve and enjoy!
Notes
Cookies can be stored covered in the refrigerator for up to 5 days.