Preheat oven to 325F and line 8"x8" baking pan with parchment paper.
Cream butter and sugars together until well combined.
Add egg and vanilla.
Sift dry ingredients together (flour, graham crumbs, baking soda and salt) then add to the butter mix. Mix until combined.
Scrap the bottom and sides of the bowl and stir in the chocolate chips.
Divide the dough into 2/3 and 1/3.
Evenly spread 2/3 of the the dough in the prepared pan and bake for 15-17 minutes. Make the Marshmallow while cookie is baking.
In a bowl of a standing mixer add 1/4 cup water and sprinkle the gelatin on top.
Place 1/4 water, corn syrup, sugar and salt in a pan and heat over the stove until mix reaches 240F.
With the mixer on low, slowly pour in the hot sugar syrup into the bowl.
Gradually increase mixer speed to high and mix until the marshmallow starts to thickened. Add the vanilla.
Grease a ruber spatula and use it to evenly spread the marshmallow over the baked cookie.
Evenly spread the remaining 1/3 of the dough into 8"x8" size square and bake for 12-14 minutes. (make sure to grease or line parchment paper on top of the pan)
Remove the cookie from the oven and let cool for 10 minutes.
When the cookie is cool break it into large pieces and places the pieces on the marshmallow. (marshmallow might be mostly set)
When marshmallow has set and the cookie is cooled, remove from the pan and slice using a large knife.