Preheat oven to 350. Mix butter, white sugar, and brown sugar together. Whisk in egg yolk and vanilla. Add baking powder, flour, salt, and graham crumbs.
Divide the dough between the ramekins to make a crust (I usually do 2 ramekins, but you can also divide between 3-4 ramekins depending on size). Top with a layer of chocolate and finish topping with a heaping pile of marshmallows.
Bake for 15 minutes, until the marshmallows are lightly browned and crispy. Allow to cool (your preference, really) and serve that gooey goodness with big spoons and glasses of milk.
