1In a medium bowl, stir together the chocolate crumbs and melted butter; press over the bottom and up the sides of a 9-inch pie plate (use a standard one, not deep dish). Refrigerate while you make the filling.
2In a medium saucepan, warm the chocolate, sugar, salt and half & half over medium heat, whisking until smooth. Add the marshmallows and cook, stirring occasionally, until the marshmallows are melted and smooth.
3Remove from the heat and if you want to speed things up, pour the mixture into a cooler bowl and/or set it in a dish of ice cubes. When it has cooled to room temperature, beat the whipping cream until stiff peaks form. Gently fold the cooled chocolate mixture into the cream until completely incorporated. Pour into the shell and use the back of a spoon to make it as swirly as you like. Refrigerate, uncovered, for at least an hour before serving. Serves 8.