1 Preheat oven to 350ºF. Grease and flour a 13x9-inch pan.2 Prepare cake mix according to package directions. Add chips and marshmallows to batter. Pour into prepared pan. Drizzle melted butter over batter. Sprinkle with sugar and top with pecans.3 Bake 45 to 55 minutes or until toothpick inserted in center comes out clean. Serve warm or cool completely in pan.