Preheat oven to 350°F and line baking sheets with parchment paper.
In a large bowl, mix melted butter, dark brown sugar, and white sugar until smooth.
Add eggs, vanilla extract, and milk. Mix until combined.
In a separate bowl, whisk flour, salt, baking soda, baking powder, cornstarch, and cinnamon.
Gradually mix dry ingredients into wet ingredients until just combined.
Fold in chocolate chips
Place a graham cracker on the parchment and add a marshmallow and Hershey on top.
Scoop the cookie dough out and place on top
Bake for 9-12 minutes or until edges are golden and centers are slightly soft.
Let cool on the pan for 5–10 minutes before transferring.
