In a large bowl, combine graham cracker crumbs, cocoa powder, sugar, melted butter, and salt. Mix until well combined and crumbly.
Press half of the crumb mixture into the bottom of a 9x9-inch baking dish to form a crust.
In a separate bowl, mix together the whipped topping and vanilla extract until smooth.
Spread the whipped topping mixture evenly over the crust in the baking dish.
Sprinkle mini marshmallows and chocolate chips evenly over the whipped topping layer.
Crumble the remaining graham cracker mixture on top of the marshmallows and chocolate chips. Press down gently to compact.
Cover the dish with plastic wrap and freeze for at least 4 hours or until firm.
Once frozen, cut into squares and serve immediately.