Preheat the oven to 375 degrees. Line a large sheet pan with parchment paper.
In the bowl of an electric mixer, cream butter with white and brown sugar until light and fluffy. Add the eggs and vanilla and mix until combined.
In a medium bowl, whisk together the flour, baking soda, sea salt and cinnamon (if using) to combine. Set aside.
Add the flour mixture to the butter mixer and combine on low speed.
Fold in the chocolate chips and marshmallows.
Lay out graham crackers squares side by side on the pans as close as possible (they should be touching). You may have to add or remove graham crackers according to how much dough you have but I usually use around 36. If you want your cookies thicker you will use more dough and less graham crackers.
Place 1 1/2 tablespoons of dough on each graham cracker square. about 1 – 1 ½ inches apart. For extra s'mores look, I like to press 1-2 mini marshmallows right on top of the dough balls.
Bake for 9-12 minutes. They will be done when the edges begin to turn golden brown. Remove to a wire rack to cool.
After cookies have cooled for about 2-3 minutes, press the Hershey’s bar pieces on to the top. You can place as many pieces or as little as you want depending how much chocolate flavor you want. I like to add a tiny sprinkle of flaky salt on top. For clean cutting make sure cookies are completely cool and cut with a sharp knife.