
In a medium bowl, stir together the graham cracker crumbs, melted butter, and sugar until combined. Firmly press the mixture into the bottom and up the sides of a 9-inch pie dish. Chill while making the filling.
Preheat the oven to 350°F. Place the chocolate chips in a medium bowl.
In a small saucepan, heat the cream over medium heat until just steaming. Pour the warm cream over the chocolate and set aside for 5 minutes. Stir gently until smooth and fully melted.
Whisk in the eggs, one at a time, until thoroughly combined. Whisk in the vanilla. Pour the chocolate mixture into the chilled crust.
Bake for 25 to 30 minutes or until the edges are set and the center jiggles slightly. Allow the pie to cool completely on a wire rack at room temperature before chilling for 2 hours or up to overnight.
Before serving, preheat the oven to Broil. Top the chilled pie with marshmallows and place under the broiler just until golden brown and toasted, 1 to 2 minutes.