Whip 100 ml cream with 1-2 tsp. sugar.
Cut 3 marshmallows into small cubes and fold into the cream.
Put 2 butter biscuits in a freezer bag, close the bag and coarsely crumble the biscuits with a dough roll.
Fill a large glass with 150 ml of cold coffee and a dash of milk, first place the marshmallow cream on top, then sprinkle with cookie crumbs.