Line a 9x13 inch baking pan with parchment so it overhangs the edges.
Lay 15 graham cracker halves in a single layer on the bottom of the pan.
In a large bowl whip together the marshmallow fluff and 2 cups of the whipped topping. Dollop it onto the graham crackers and spread into an even layer.
Drizzle chocolate sauce over the whipped topping.
In a second large bowl, mix cold milk with pudding with a hand mixer on medium speed for 1 minute. Fold in the remaining whipped topping. Pour over the marshmallow fluff and chocolate sauce.
Place the remaining graham crackers on top.
Freeze for 4-5 hours or until firm enough to cut.
Use the parchment to pull out of the pan. Trim the excess filling from the edges and cut into 15 squares.
Serve cold right away or wrap individually and freeze until you are ready to serve.
Notes
Keep s'mores bars in an airtight container in the freezer for up to 1 month.