Spray a 9-inch springform pan with cooking spray. Combine the graham-style crumbs with the melted butter, stirring to combine. Press firmly into the bottom of the prepared pan. Place in the freezer for 10-15 minutes.

While the pan is in the freezer, let the ice cream sit at room temperature to soften. Scoop the ice cream on top of the crust and smooth the top with a spatula. Place back in the freezer until the ice cream has hardened, at least 4 hours or up to 3 days.

Before serving, preheat the broiler and place the top rack 6 inches from the top of the oven. Spread the marshmallows over the top of the cake in an even layer. Place under the broiler for about 2 minutes or until the marshmallows have browned. Watch carefully to keep from burning.

Serve cake immediately or place back in the freezer until ready to serve.