Melt the unsalted butter in the microwave or stovetop.
Add the white sugar, and brown sugar, and mix until the butter is fluffy.
Add the eggs and vanilla to the mixture and mix on medium speed for another 3-4 minutes. The batter should be light-colored and fluffy at this point.
Add in the dry ingredients (flour, salt, and baking soda) and mix well until all the dry mixture is combined with the wet ingredients just until combined. Don’t overmix.
Add in the mini marshmallows, milk chocolate chips, and chopped graham crackers and fold into the rest of the batter.
Divide the batter into equal balls of dough (I use an ice cream scooper to help). The dough usually makes about 16 cookies, depending on the size.
Place mixture in the fridge for at least 2 hours (ideally overnight).
Pre-heat oven to 350ºF degrees.
On a cookie sheet lined with parchment paper or a silicone mat, place cookie dough balls at least 1.5 inches apart.
Top with extra mini marshmallows
Place cookie sheet in the oven and bake for 8-12 minutes. The sides should start to brown on the sides but the center will look soft.
Remove from the oven.
Using a circle cookie cutter or lid, shape the cookies if they are not perfectly round (if desired)
Leave in the cookie sheet to cool for at least 20 minutes.
The cookies will be too soft when they are fresh from the oven and will harden as they cool.