In a large bowl, using an electric mixer, cream together the room temp butter, brown sugar, and white sugar until lighter and fluffy (3-5 minutes – don't skimp on this step!). Add in the egg plus egg yolk and beat until smooth. Then, in a small bowl, stir together the vanilla extract and the instant coffee granules until dissolved, then pour into the cookie dough and beat until combined. Add in the flour (and xanthan gum if needed), unsweetened dutched cocoa powder, regular unsweetened cocoa powder, baking soda, and salt and mix by hand with a wooden spoon or spatula until fully combined (it will be stiff). Finally, mix in 1 cup (160g) of the chopped milk chocolate, 1 cup (100g) of the chopped gluten free graham crackers, and 1 cup of mini marshmallows until they're fully distributed. Scoop dough into a smaller bowl, cover with plastic wrap, and chill in the fridge for 1 hour.