Place the graham crackers into a blender or food processor. Pulse or blend until they are the texture of sand.

Measure 1 cup of the graham cracker crumbs and whisk together with the flour, cornstarch, baking soda and salt. Set aside.

Add the soft butter, brown and white sugar to the bowl of a stand mixer, or a large mixing bowl. Beat with the paddle attachment, or a hand mixer, until the butter and sugars have combined and are fluffy, about 1 to 2 minutes.

Scrape the sides of the bowl and add the eggs, one at a time, stirring well between each addition.

Mix in the vanilla.

Slowly stir in the dry ingredients until the dough has formed.

Fold in the chocolate chips and marshmallows.

Scoop the dough into 1/4 cup full and roll into a ball.

Place on a small tray and repeat with the remaining dough.

Chill for 30 minutes in the freezer, or up to 2 days covered in the refrigerator.

While the dough is chilling, preheat the oven to 325 degrees and line two baking trays with parchment or silicone baking mats.

Once the dough has chilled, place 2-3 inches apart on the prepared trays.

Bake 17-20 minutes, or until the edges of the dough have slightly browned.

Allow the cookies to cool on the trays for 15 minutes.