Remove the graham cracker crust from the oven (it should be crisp and no longer loose and sandy) and allow it to cool for about 5 minutes.
After the crust is slightly cooled, drizzle the sweetened condensed milk over the entire crust, carefully spread the sweetened condensed milk with a spoon or offset spatula. Make sure to cover every inch of the crust!
Add half of the marshmallows over the crust, then sprinkle all of the chocolate chips over that.
Next, crumble the graham cracker sheets into small pieces and sprinkle those on top of the marshmallows and chocolate chips.
Finish it off by adding the last half of the marshmallows to the top.
Bake in a 350 degree Fahrenheit oven for about 10-15 minutes until the marshmallows begin to brown on top. If you are not seeing a lot of caramelization, you can set your oven to the broil setting for about 2-3 mintues. Check them every 30 seconds if you do use the broiler method as the marshmallows can go from brown to burnt very very quickly!
Once the marshmallows have nicely caramelized, take the pan out of the oven and allow to cool for 2-3 hours. Cut into squares and enjoy! Depending on the size you cut the bars, this recipe makes 36-55 bars. They will keep well wrapped in aluminum foil at room temp for up to 5 days (if they last that long)!