Preheat your oven to 375°F. Line two baking sheets with parchment paper and set aside.
In a medium bowl, whisk the flour, cocoa, instant coffee, baking soda, and salt together. Set aside.
In a large mixer bowl with your paddle attachment, beat the sugars & butter until light & fluffy.
Add in the eggs. Beat well, then add in the vanilla.
Add the flour mixture slowly to the butter mixture and mix until thoroughly incoporated.
Place the 1/2 cup of granulated sugar in a small bowl and set aside.
Take 2 tablespoons of cookie dough and then wrap it completely around half of a large marshmallow. Roll the dough into a ball around the marshmallow so that the marshmallow is completely covered.
Roll the cookie ball in the sugar mixture then place on parchment paper lined cookie sheet 2 inches apart.
Place on the prepared baking sheets at least 1.5 inches apart. If the cookie dough seems warm, cool the cookies on the cookie sheet for 5 minutes in the fridge, then bake.
Bake for 10-12 minutes until the edges of the cookies are baked and set. Make sure the marshmallow doesn't bubble out of the cookies too much, if they start to explode remove them from the oven.
Cool on the cookie sheets.
Store in a closed container at room temperature for up to 4 days, or freeze in an airtight container for up to 3 months.
Notes
Try using flavored marshmallows in the center, like strawberry!