1. Preheat oven to 350℉ and line a 9 x 13 x 2-inch baking pan with parchment paper or non-stick foil.
2. In a large bowl mix together the graham cracker crumbs, melted butter and salt. Pour into prepared pan and press evenly into the bottom. Bake for 15 - 20 minutes and crust is lightly golden. Cool completely.
3. Place both bittersweet and milk chocolate chips in a large bowl. In a medium saucepan, bring heavy cream to a boil. Remove pan from the heat and pour the cream over the chocolates. Let the mixture sit for 5 minutes before whisking until smooth.
4. Add mini-marshmallows and graham cracker pieces, stirring well to ensure all the pieces are evenly coated with the chocolate ganache. Pour mixture evenly over cooled graham cracker crust. Sprinkle the top of cookie bars with the smoked salt. Refrigerate for 1 -2 hours until filling is firm and set.