Preheat oven to 350 degrees
Arrange whole graham crackers in a single layer in a greased 13x9-in. baking pan. Prepare the brownie batter according to package directions. Spread over crackers.
Bake at 350Â° for 25-30 minutes or until a toothpick inserted near the center comes out clean. Sprinkle with marshmallows, chocolate chips and chunked-up graham crackers. Bake 5 minutes longer or until marshmallows are slightly puffed and golden brown. Cool on a wire rack before cutting.