Roughly chop the Graham crackers and Hershey's bar, then split the miniature marshmallows in half. All these marshmallows are among the greatest regions of the cookie however they will puff up and get somewhat out of control in case you don't halve them.
Blend the flour, salt, baking powder, baking soda, and cornstarch in a bowl then drizzle together and put aside.
Employing a hand or stand mixer, beat sugar and butter in a bowl until creamy, about 2 minutes. Add in vanilla and egg and till blended. Scrape down the bowl and mix once again.
Reserve a few of those ripped marshmallows and put aside then insert the rest of the marshmallows, chocolate chips, along with Graham crackers into the dough and blend on low until just blended (don't over-beat).
Refrigerate dough for an hour or so longer. Portion out about two tbsp sized pieces of bread. Roll into balls and put onto a parchment-lined baking sheet, spacing about 2 inches apart.
Bake at 350° for 2 minutes then high the biscuits with the booked marshmallow and Hershey's bar bits then come back to the oven for 2-3 minutes to complete baking. IF some cookies had a blowout due to a couple of too many marshmallows for you can corral them back using a round cookie cutter or a knife.
Leave pan to cool fully