Crush 4 graham crackers into fine crumbs and roughly chop rest of Graham crackers and Hershey's bar into small pieces.
Tear the mini marshmallows in half. This will help to prevent blowout in the cookies.
In a bowl combine the flour, salt, baking powder, baking soda, and cornstarch in a bowl then whisk together to this add graham cracker crumbs and mix well once again and set aside.
Using a stand or hand mixer, beat butter and both granulated sugar and white sugar in a bowl until creamy, about 2 minutes. Add in egg and vanilla and until combined. Scrape the bowl down and mix once more.
To this gradually add flour mixture to butter mixture, beating on low speed until just combined.
Set aside few torn marshmallows, chocolate bar and graham cracker pieces. Then fold in remaining marshmallows, chocolate chips . Use spatula here thus you won’t over beat the dough.
Heatoven to 350°F. Portion out roughly two tablespoon sized pieces of dough.Roll into balls and place on a parchment-lined baking sheet, spacing about 2inches apart. Top the cookie dough with reserved graham cracker, Hershey’s bar, and marshmallowpieces.
Bakeat 350°F for 8-10 minutes or until sides are lightly brown
Leave it in the pan to cool completely. Don’t try to take it out as it will still soft.