Preheat the oven to 375℉
Beat butter and sugars in a mixer.
Add egg and vanilla, scraping sides.
Add flour, baking soda and salt.
Add chocolate chips.
Scoop 3 ounces of dough out and stuff 5 mini marshmallows in the center enclosing them tightly. Lay on parchment paper.
Bake for about 10-11 mins. Keep an eye on them the first time as everyone's oven is different! Use a large cookie cutter to help round the cookie when out of the oven.
Cool a few mins and drizzle with melted chocolate. Sprinkle on some smashed graham crackers, if desired.