Preheat your oven to 350°F (175°C). In a mixing bowl, combine crushed graham crackers, melted butter, and a pinch of salt. Press firmly into an 8-inch square baking dish. Bake for 10 minutes or until golden brown. Allow to cool completely.

In a medium saucepan over medium heat, warm heavy cream until steaming, about 3-5 minutes. Pour it over chopped chocolate bars and let it sit for a few minutes, then stir until smooth and glossy to form ganache.

Gently fold in large marshmallows into the ganache mixture until evenly coated. Mix gently to avoid breaking the marshmallows.

Pour the ganache and marshmallow mixture over the cooled crust, spread evenly, cover with plastic wrap, and place in the freezer for at least 4 hours or overnight.

After freezing, let the dessert sit at room temperature for 5-10 minutes before slicing. Cut into squares and garnish if desired.