Preheat the oven to 375 degrees F. Lightly grease a removable-bottom tart pan with butter, oil, or cooking spray. Combine the graham cracker crumbs, butter, and brown sugar in a small bowl; mix evenly. Press the crumb mixture evenly into the bottom and halfway up the rim of the assembled pan. Cover the crust with an even layer of chocolate chips and cover those with the marshmallows. Bake for 15 to 20 minutes, or until the marshmallows are melted and golden brown. Remove the pizza and cool on a wire rack for 5 minutes. Then, carefully remove the tart ring. Slice and serve.