For the graham cracker crust:
4 cups graham cracker crumbs
1/2 cup sugar
10 tablespoons unsalted butter, melted
For the marshmallow topping:
1 cup sugar
1/2 cup water
4 large egg whites
1/2 teaspoon cream of tartar
To make the graham cracker crust: Combine all ingredients and press mixture into bottom and up the sides of an 8-inch springform pan. Transfer to oven and bake at 375°F for 7 to 9 minutes, or until crust deepens in color. Remove from oven and transfer to a wire rack to cool completely.
To make the marshmallow topping: Place sugar and water into a saucepan with a candy thermometer attached to the side of the pan. Bring the mixture to a boil and cook until the syrup reaches 240°F; set aside.
Place egg whites and cream of tartar in a stand mixer bowl fitted with a whisk attachment and beat on medium until soft peaks are formed. With the mixer still running, slowly drizzle syrup into egg mixture. Continue beating until stiff peaks form.
Assembly: Using an ice cream scoop, randomly drop scoops of chocolate and vanilla ice cream over the graham cracker crust. Sprinkle and press in broken-up pieces of graham cracker. Continue to layer like this until the pan is filled. Transfer to freezer and chill until hardened, about two hours.
Remove from freezer and spread marshmallow topping on top, then using a kitchen torch, toast marshmallow topping. Serve immediately.