In the bowl of a stand mixer or a large bowl with hand mixer, beat together butter and both sugars until light and fluffy, about 2-3 minutes.
Add in vanilla and milk and then mix in the flour and salt. Beat on low speed until incorporated.
Line up graham crackers and spread about a tablespoon of dough onto 12 of the graham cracker halves. Place a couple squares of chocolate on top of the cookie dough.
Toast marshmallows using a kitchen torch or over the flame of a gas stove and place on top of chocolate. Alternatively, you can put the marshmallows on the graham crackers without cookie dough and place under broiler for 30-60 seconds or in the microwave (they just won't get charred in the microwave).
Top with remaining graham cracker halves and smoosh together a bit. Enjoy!