In the bowl of a stand mixer, add the egg, yolk, vanilla and both kinds of sugar. Whip on high for ten minutes to create a frothy meringue like texture.
In a separate bowl, add the flour, cocoa powder, espresso powder and salt. Stir until combined.
In a microwave safe bowl, add the chocolate and the stout. Microwave on high for 30 seconds, stir and repeat until melted.
Mix the chocolate into the eggs until combined.
Sprinkle the flour, cocoa powder and espresso powder over the chocolate/egg mixture, stir until just combined. Place in the fridge and allow to chill until set up enough to scoop, about 30 minutes. Preheat oven to 375
Line baking sheets with parchment paper. Using a cookie scoop, drop equal amounts of dough evenly space on the cookie sheet.
Bake for 9-11 minutes, don't over bake. Allow to cool.
In the bowl of a stand mixer add the whipped cream, powdered sugar and cocoa powder. Beat on high until stiff peaks form, slowly pour the 3 tablespoons stout into the mixer, beat until beer is incorporated into the whipped cream.
Spoon the whipped cream into the cookies. Refrigerate until firm, about 30 minutes and up to 24 hours. Allow to sit at room temperature for 10 minutes before serving.